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Fat metabolism in insects
Abstract
The study of fat metabolism in insects has received considerable attention over the years. Although by no means complete, there is a growing body of information about dietary lipid requirements, and the absolute requirement for sterol is of particular note. In this review we (a) summarize the state of understanding of the dietary requirements for the major lipids and (b) describe in detail the insect lipid transport system. Insects digest and absorb lipids similarly to vertebrates, but with some important differences. The hallmark of fat metabolism in insects centers on the lipid transport system. The major lipid transported is diacylglycerol, and it is carried by a high-density lipoprotein called lipophorin. Lipophorin is a reusable shuttle that picks up lipid from the gut and delivers it to tissues for storage or utilization without using the endocytic processes common to vertebrate cells. The mechanisms by which this occurs are not completely understood and offer fruitful areas for future research.
... Consequently, although insects generally grow faster when fed high protein diets, the protein economy of a production facility may be less efficient. Comparatively, lipids are stored directly proportional to the amount of energy they contain from lipids and carbohydrates [45]. Protein is utilized most efficiently for tissue growth at the highest possible ratio, while carbohydrates and lipids are utilized for energy, as this produces the most rapid increase in protein body mass [26,45]. ...
... Comparatively, lipids are stored directly proportional to the amount of energy they contain from lipids and carbohydrates [45]. Protein is utilized most efficiently for tissue growth at the highest possible ratio, while carbohydrates and lipids are utilized for energy, as this produces the most rapid increase in protein body mass [26,45]. Rho and Lee (2016) declared that, for Tenebrio molitor larvae, the optimal protein to carbohydrate ratio lies around 1:1 for optimal growth [46]. ...
... This effect has also been demonstrated in another study [74], whereas the fat content of Tenebrio molitor was higher on carbohydrate-rich diets. A diet rich in carbohydrates and lipids can contribute to produce insects that are lipid-rich, while a diet rich in protein enables insects to be lean [45,72]. Tenebrio molitor larvae need a high content of carbohydrates in their diet, with an optimal range of 80-85% [25]. ...
The use of insects as livestock feed is becoming increasingly accepted because they provide an important source of protein. The purpose of this study was to investigate the chemical composition of mealworm larvae (Tenebrio molitor L.) reared on a range of diets that differed in nutritional composition. Focus was placed on the influence of dietary protein content on larval protein and amino acid composition. For the experimental diets, wheat bran was chosen as the control substrate. The following types of flour-pea protein, rice protein, sweet lupine, and cassava, as well as potato flakes, were mixed with wheat bran and used as the experimental diets. An analysis of the moisture, protein, and fat content was then carried out for all diets and larvae. Furthermore, the amino acid profile was determined. It was shown that supplementing the feed with pea and rice protein was most suitable in terms of high protein yield in larvae (70.9-74.1% dry weight) with low fat content (20.3-22.8% dry weight). The total amino acid content was highest in larvae that were fed with a mixture of cassava flour and wheat bran (51.7 ± 0.5% dry weight), as well as the highest content of essential amino acids (30.4 ± 0.2% dry weight). Moreover, a weak correlation between larval protein content and diet was identified, yet a stronger influence of dietary fats and carbohydrates on larval composition was found. This research could result in improved formulations of artificial diets for Tenebrio molitor larvae in the future.
... In addition, they have a high protein (25-75%) and fat (10-70%) content in dry matter and are rich in essential amino acids and polyunsaturated fatty acids [6][7][8]. The composition and growth of mealworm larvae depend on rearing conditions, e.g., environmental influences such as temperature and relative humidity [9]. Their diet, too, has a significant influence, whereby the nutrient composition of mealworm larvae can be regulated by targeted feeding. ...
... For example, supplementing the diet with flaxseed meal and oil increased the content of α-linolenic acid in mealworm larvae [8,10]. Therefore, research on nutritional requirements, transport of nutrients, and metabolism, especially dietary lipid utilization and storage, has become increasingly important [9]. Consequently, and for food safety and quality control reasons, it is beneficial to monitor nutritional parameters such as fat and fatty acid content during rearing. ...
... FAs perform several important functions in insects by acting as precursors for the synthesis of pheromones, an energy reserve, and an important component for the performance of metamorphosis [37,38]. The main FAs detected in mealworm larvae were, in particular, oleic, linoleic, and palmitic acid and are similar to those reported in previous studies [9,39]. Normally, commercially produced insects consist of a high amount of oleic and linoleic acid due to feeding with grains and grain by-products that are generally high in oleic and linoleic acid [40,41]. ...
Several studies have shown that mealworms (Tenebrio molitor L.) could provide animals and humans with valuable nutrients. Tenebrio molitor larvae were studied to determine whether their rearing diets affected their fat and fatty acid content and to ascertain if it is possible to detect the changes in the larval fat composition using near-infrared reflectance spectroscopy (NIRS). For this reason, a standard control diet (100% wheat bran) and an experimental diet, consisting of wheat bran and the supplementation of a different substrate (coconut flour, flaxseed flour, pea protein flour, rose hip hulls, grape pomace, or hemp protein flour) were used. The results showed lesser weight gain and slower growth rates for larvae raised on diets with a high fat content. A total of eight fatty acids were identified and quantified, where palmitic, oleic, and linoleic acids were the most prevalent and showed a correlation between larval content and their content in the rearing diets. There was a high content of lauric acid (3.2-4.6%), myristic acid (11.4-12.9%), and α-linolenic acid 8.4-13.0%) in mealworm larvae as a result of the high dietary content of these fatty acids. NIR spectra were also influenced by the fat and fatty acid composition, as larval absorbance values differed greatly. The coefficient of the determination of prediction (R2P) was over 0.97, with an RPD value of 8.3 for the fat content, which indicates the high predictive accuracy of the NIR model. Furthermore, it was possible to develop calibration models with great predictive efficiency (R2P = 0.81-0.95, RPD = 2.6-5.6) for all fatty acids, except palmitoleic and stearic acids which had a low predictive power (R2P < 0.5, RPD < 2.0). The detection of fat and fatty acids using NIRS can help insect producers to quickly and easily analyze the nutritional composition of mealworm larvae during the rearing process.
... Body condition generally refers to the energetic state of an animal and assumes that individuals with greater fat reserves are in better condition because they have more resources to fuel various fitness-related functions. In insects, the fat body is responsible for the synthesis and storage of energy-rich molecules such as glycogen and lipid, among others (Arrese & Soulages, 2010;Canavoso et al., 2001;Chapman, 1998;Downer & Matthews, 1976;Skowronek et al., 2021). Fat body components are mobilized for a wide variety of conditions and processes such as flight, immunity, starvation and embryogenesis. ...
... Fat body components are mobilized for a wide variety of conditions and processes such as flight, immunity, starvation and embryogenesis. During embryogenesis, the fat body produces considerable amounts of the major egg protein vitellogenin, which is taken up by the developing oocytes (Downer & Matthews, 1976;Hoffmann, 1995;Jacome et al., 1995;Kawooya & Law, 1988;Ziegler & Ibrahim, 2001) and supplies the major portion of lipid in the oocyte (Canavoso et al., 2001;Downer & Matthews, 1976;Jacome et al., 1995;Jouni et al., 2003). ...
Keywords: body condition cricket fat load fecundity metabolism Female fecundity is dependent on age and mated status. Young female insects accumulate considerable fat stores to fuel energetically expensive ovary development and egg production. Consequently, younger females are expected to have more stored fat than older females while the latter should have larger eggloads than the former. Mating is expected to increase fecundity because male ejaculates contain fecundity-enhancing substances that stimulate egg development, ovulation and oviposition. We experimentally tested the effect of female age (young versus old) and mated status (virgin versus mated) on fat and eggloads in female Gryllus firmus field crickets (Orthoptera: Gryllidae), in addition to testing the prediction that young or mated females have higher resting metabolic rates (RMR) than old or virgin females because the former should be significantly more engaged in the energetically expensive activity of egg production than the latter. As predicted, we found that young females had more fat and fewer eggs than old females and that fat loads negatively correlated with fecundity across all females. Young females also exhibited higher RMR, as expected if egg production is energetically costly. Contrary to expectation, however, mated status had little effect on fat load, egg production or RMR. That mating had little effect on total egg production (i.e. stored and oviposited eggs) challenges the hypothesis that male fecundity-enhancing substances in the ejaculate stimulate egg production. Our experiment also permitted us to examine the validity of two popular indices of body condition, the scaled mass index (SMI) and residual body mass (R i). Neither index accurately represented the true treatment effects of age and mated status on fat load; however, the SMI reflected true fat content in young, but not old, females.
... Studies have shown that protein content affects the reproduction, physiological function, immunity, and larval development of bees [14][15][16][17][18][19]. Lipids play a vital role in bee development, as the metabolism of lipids is involved in various life activities of bees, such as growth and development [20], molting hormone production [21], learning ability improvement [22], gland formation [21] and brooding work [23]. Although pollen constitutes a nutritional resource for bumblebees as an essential source of proteins and lipids, the content and proportion of these nutrients differ between source plants. ...
... Studies have shown that protein content affects the reproduction, physiological function, immunity, and larval development of bees [14][15][16][17][18][19]. Lipids play a vital role in bee development, as the metabolism of lipids is involved in various life activities of bees, such as growth and development [20], molting hormone production [21], learning ability improvement [22], gland formation [21] and brooding work [23]. Although pollen constitutes a nutritional resource for bumblebees as an essential source of proteins and lipids, the content and proportion of these nutrients differ between source plants. ...
Pollen is a major source of proteins and lipids for bumblebees. The nutritional content of pollen may differ from source plants, ultimately affecting colony development. This study investigated the foraging preferences of Bombus terrestris in regard to four pollen species, i.e., oilseed rape, wild apricot, sunflower, and buckwheat, under laboratory conditions. The results show that B. terrestris diversified their preference for pollens; the bumblebees mostly preferred wild apricot pollen, whereas sunflower pollen was the least preferred. The colonies fed on a mixed four-pollen diet, with a protein–lipid ratio of 4.55–4.86, exhibited better development in terms of the number of offspring, individual body size and colony weight. The colonies fed with buckwheat and sunflower pollens produced a significantly lower number of workers and failed to produce queen and male offspring. Moreover, wild apricot pollen had the richest protein content (23.9 g/100 g) of the four pollen species, whereas oilseed rape pollen had the highest lipid content (6.7 g/100 g), as revealed by the P:L ratios of wild apricot, sunflower, buckwheat, and oilseed rape, which were 6.76, 5.52, 3.50, and 3.37, respectively. Generally, B. terrestris showed feeding preferences regarding different pollens and a mixture of pollens, which ultimately resulted in differences in colony development. The findings of this study provide important baseline information to researchers and developers of nutritive pollen diets for bumblebees.
... Fat reservoirs are essential in holometabolous insects, as they are also used during metamorphosis [5]. TAGs constitute over 90% of lipids stored in fat body tissue [2]. This lipidic content is consistent with our results because TAG levels in the fat body were significantly higher than in haemolymph in almost all experimental variants and samples from insects treated with GAs ( Figure 1). ...
... The primary sterol is cholesterol, which builds cell membranes and is a precursor of ecdysteroid hormones. Many insects can convert plant sterols to cholesterol, e.g., sitosterol, campesterol, stigmasterol, and ergosterol [2]. After GA application, sterols exhibited similar changes to FA-their content usually decreased in haemolymph, while increasing in the fat body 24 h after 10 −8 M GA application (Figures 2-4). ...
Glycoalkaloids (GAs) are produced naturally by plants and affect insect survivability and fertility. These compounds can be considered potential bioinsecticides; however, the mechanisms and effects of their action remain undiscovered. As lipids are essential molecules for the proper functioning of an insect organism, this research aimed to determine the effects of GAs on the lipid metabolism of the Tenebrio molitor beetle. Solanine, chaconine, tomatine, and tomato leaf extract were applied to larvae by injection at two concentrations, 10−8 and 10−5 M. Then, the tissue was isolated after 2 and 24 h to determine the levels of free fatty acids, sterols and esters using the GC‒MS technique. Moreover, the triacylglyceride level and the activity of the key β-oxidation enzyme, 3-hydroxyacyl-CoA dehydrogenase (HADH), were measured. The results indicate that GAs affect the content and composition of lipid compounds in the beetles’ haemolymph and fat bodybodybodies. The effects depend on the GA concentrations, incubation time, and kind of tissue. Moreover, the tested compounds decrease HADH activity, especially in the fat body, which may affect energy production. To our knowledge, this is the first study concerning lipid metabolism in T. molitor after GA application. Our results provide some insights into that topic.
Citation: Winkiel, M.J.; Chowański, S.; Gołębiowski, M.; Bufo, S.A.; Słocińska, M. Solanaceae Glycoalkaloids Disturb Lipid Metabolism in the Tenebrio molitor Beetle. Metabolites 2023, 13, 1179.
... TAGs are the predominant lipid form in insects, functioning as energy storage molecules and as precursors for other molecules, such as semiochemicals [31]. Table 2). ...
... PC and TAG were the main lipids in the mandibular gland, consistent with our previous research [54]. TAGs are the predominant form of lipids in insects, functioning as energy storage molecules during non-feeding periods and longdistance flight [55,56] and as precursors for other molecules, such as semiochemicals [31]. As important neutral lipids, TAGs contain a glycerol backbone and three FA chains [51]. ...
This study aimed to assess the impact of oleic acid (OA) supplementation on the biosynthesis of 10-hydroxy-2-decenoic acid (10-HDA) in Apis mellifera ligustica. In experiment 1, varying concentrations of OA (2%, 4%, 6% and 8%) were added to an artificial diet for newly emerged bees reared in cages. Analysis of 10-HDA content and gene expression in the mandibular gland (MG) revealed that the 8% OA treatment had the greatest impact on promoting the synthesis of 10-HDA. Subsequent investigations utilized RNA-seq and lipidomics to characterize the molecular signature in the MG after feeding the 8% OA diet. Phosphatidylcholine (PC) and triacylglycerol (TAG) were found to be the predominant lipids in the MG of worker bees. A total of 154 TAGs were identified, with TAG (18:1-18:1-18:1) exhibiting the highest abundance, which increased by 1.5 times. The major TAG species contained palmitic acid (16:0) and oleic acid (18:1) in their structure, which was associated with fatty acid composition of diet. The increase in abundance of main TAGs may be attributed to the upregulation of glycerol-3-phosphate acyltransferase (Gpat) and glycerol kinase (GK) gene expression at the transcriptional level. The upregulation of differentially expressed genes (DEGs) related to carbohydrate metabolism may contribute to meeting the heightened metabolic demands of the MGs in worker bees. Royal jelly (RJ) samples from bee colonies fed with the 8% OA diet exhibited higher 10-HDA level than RJ collected from bee colonies fed with the artificial diet. These results indicate that 8% OA addition in the diet enhanced biosynthesis of 10-HDA in the mandibular gland, which was accompanied by significant and highly species-selective remodeling of TAGs.
... However, the importance of LCFAs is also recognized as an important factor affecting herbivorous insect behavior. LCFAs in leaves function not only as a nutritional factor (Canavoso et al. 2001;Eigenbrode and Espelie 1995;Friend 1958) but also as an olfactory cue to insects (Mukherjee et al. 2014;Schoonhoven et al. 2005). For example, major LCFAs, particularly unsaturated LCFAs, oleic, linolenic and linoleic acids, can promote acceptance on host plants and the growth of insects grazing the leaves (Erb et al. 2013;Ishangulyyeva et al. 2016). ...
... Besides the olfactory attractiveness, the relation between LCFAs and herbivorous feeding is also important (Eigenbrode and Espelie 1995). Many species of insects, including Coleoptera, have a dietary requirement for polyunsaturated fatty acids, such as linoleic and linolenic acids, which influence the larval growth and adult fecundity (Canavoso et al. 2001). Previous research based on the same FACE system found that the grazing damage (Agathokleous et al. 2017) and the development of insects (Abu ElEla et al. 2018) was significantly affected by direct or indirect effects of O 3 . ...
Long-chain fatty acids (LCFAs) in leaves have attracted attention as nutritious phytochemicals and olfactory signals that influence the behavior and growth of herbivorous insects. In recognition of the negative effects of increasing tropospheric ozone (O3) levels on plants, LCFAs can be altered through peroxidation by O3. However, how elevated O3 changes the amount and composition of LCFAs in field-grown plants is still unknown. We investigated palmitic, stearic, oleic, linoleic, linolenic LCFAs in the two leaf types (spring and summer) and two stages (early and late stage after expansion) of Japanese white birch (Betula platyphylla var. japonica) after a multi-year O3 exposure on the field. Summer leaves exhibited a distinct composition of LCFAs under elevated O3 at the early stage, whereas both stages of spring leaves did not exhibit significant changes in LCFAs composition by elevated O3. In the spring leaves, the amounts of saturated LCFAs significantly increased at the early stage, however, the amount of total, palmitic, and linoleic acids at the late stage were significantly decreased by elevated O3. Summer leaves had a lower amount of all LCFAs at both leaf stages. Regarding the early stage of summer leaves, the lower amount of LCFAs under elevated O3 was possibly due to O3-suppressed photosynthesis in the current spring leaves. Furthermore, the decrease ratio of spring leaves over time was significantly increased by elevated O3 in all LCFAs, whereas summer leaves did not exhibit such an effect. These findings suggest that further studies should be conducted to reveal the biological functions of LCFAs under elevated O3, considering the leaf type- and stage-dependent changes of LCFAs.
... The fat body is responsible for immune function in insects [23]. This organ is considered equivalent to the vertebrate liver and adipose tissues [24,25]. The mammalian liver contributes are displayed as the average ± standard error of three biological replicates, with technical replicates. ...
... bmGCL: Bombyx mori glutamate-cysteine ligase to in GSH homeostasis [26]. The high level of expression of bmGCL in fat body concurred with previous reports [23][24][25][26], as the production of GSH by bmGCL contributes to the control of cellular redox systems. Interestingly, a low level of bmgcl mRNA was detected in the silk gland. ...
Glutamate-cysteine ligase (GCL) is a crucial enzyme involved in the synthesis of glutathione (GSH). Despite various studies on glutathione transferase, and its essential role in detoxification and resistance to oxidative stress, GSH synthesis has not been described in Bombyx mori (silkworms) to date. Silkworms form part of the lepidopterans that are considered as a model of agricultural pests. This study aimed to understand the GSH synthesis by GCL in silkworms, which may help in developing insecticides to tackle agricultural pests. Based on the amino acid sequence and phylogenetic tree, the B. mori GCL belongs to group 2, and is designated bmGCL. Recombinant bmGCL was overexpressed and purified to ensure homogeneity. Biochemical studies revealed that bmGCL uses ATP and Mg²⁺ to ligate glutamate and cysteine. High expression levels of bmgcl mRNA and GSH were observed in the silkworm fat body after exposure to insecticides and UV-B irradiation. Moreover, we found an increase in bmgcl mRNA and GSH content during pupation in the silkworm fat body. In this study, we characterized the B. mori GCL and analyzed its biochemical properties. These observations indicate that bmGCL might play an important role in the resistance to oxidative stress in the silkworms.
... The fat body is responsible for immune function in insects [22]. The fat body in insects is considered equivalent to the vertebrate liver and adipose tissue [23,24]. The mammalian liver contributes to in GSH homeostasis [25]. ...
... The mammalian liver contributes to in GSH homeostasis [25]. The highest expression of bmGCL in fat body is concured with previous reports [22,25,24,23], as the production of GSH by bmGCL contributes to the control of cellular redox. Interestingly, there was a low level of bmgcl mRNA detected in the silk gland. ...
Background: Glutamate cysteine ligase (GCL) is a crucial enzyme involved in the synthesis of glutathione (GSH). Despite various studies on glutathione transferase and its essential role in detoxification and resistance to oxidative stress, GSH synthesis has not been described in silkworms to date. Silkworms form part of the lepidopterans that are considered as a model of agricultural pests. This study aimed to understand the GSH synthesis through the GCL in silkworms so that insecticides can be formulated to tackle agricultural pests.
Methods and Results: Based on the amino acid sequence and phylogenetic tree, this GCL belonged to group 2 and designated bmGCL. Recombinant bmGCL was overproduced and purified to ensure homogeneity. Biochemical studies revealed that bmGCL uses ATP and Mg²⁺ to ligate glutamate and cysteine, respectively. High expression levels of bmgcl mRNA and GSH were observed in the silkworm fat body after exposure to insecticides and UV-B. Moreover, we found an increase in bmgcl mRNA and GSH content during pupation in the silkworm fat body.
Conclusion: In this study, we found GCL in the silkworm Bombyx mori and its biochemical properties were investigated. These observations indicate that bmGCL might play an important role in the resistance to oxidative stress in B. mori.
... Indeed, the digestive and neuroendocrine systems of fruit flies are highly conserved in vertebrates and all the key organs in flies that control metabolism have counterparts in humans ( Figure 1). For example, the fat bodies are similar to human white fat tissue and liver, Malpighian tubules are similar to human kidneys, oenocytes are similar to human hepatocytes, insulin-producing cells in the pars intercerebralis are similar to islets in the human pancreas, and the corpus cardiacum system is similar to the human hypothalamus-pituitary system [38][39][40]. Accordingly, the Drosophila digestive tract is now at the cutting edge of research [41] and is important for the analysis of obesity-related diseases in humans [42]. ...
... Pyruvate plays a key role in glycolysis and also links to other metabolic pathways in insects and humans ( Figure 3). Drosophila fat bodies store glycogen in addition to lipids [39]. The regulation of sugar and fat storage is very similar in flies and humans. ...
Insects are the most diverse organisms on earth, accounting for ~80% of all animals. They are valuable as model organisms, particularly in the context of genetics, development, behavior, neurobiology and evolutionary biology. Compared to other laboratory animals, insects are advantageous because they are inexpensive to house and breed in large numbers, making them suitable for high-throughput testing. They also have a short life cycle, facilitating the analysis of generational effects, and they fulfil the 3R principle (replacement, reduction and refinement). Many insect genomes have now been sequenced, highlighting their genetic and physiological similarities with humans. These factors also make insects favorable as whole-animal high-throughput models in nutritional research. In this review, we discuss the impact of insect models in nutritional science, focusing on studies investigating the role of nutrition in metabolic diseases and aging/longevity. We also consider food toxicology and the use of insects to study the gut microbiome. The benefits of insects as models to study the relationship between nutrition and biological markers of fitness and longevity can be exploited to improve human health.
... In insects, fat bodies serve a variety of essential functions. The majority of lipids are stored in the fat body, analogous to the roles of vertebrate adipose tissue and liver (Canavoso et al. 2001;da Cunha et al. 2006). Essential physiological functions supported by the fat body include survival, nutrient sensing, lipid storage, metabolism, innate immunity, and endocrine signaling to the brain and reproductive organs (Skowronek et al. 2021). ...
Polygonia c-aureum adults of both sexes have two types of fat bodies (small spherical or large long and slender). This butterfly overwinters as adults, and adult diapause is maintained by short day-length (SD) and terminated by long day-length (LD), aging and/or high temperatures. Under SD, both types of fat bodies increased in size with increased adult age until day 40 and then leveled off. Under LD, both fat bodies initially increased but then decreased in size. Since applying JH analog (methoprene) did not affect male fat body development while the accessory glands and simplex developed, we conclude that it was flight behavior, rather than the development of those reproductive organs, that strongly affected the consumption of fat body under virgin conditions. When butterflies of both sexes were kept at 21℃ under SD for 15, 30, or 45 days of adult life and transferred to 5℃ (complete darkness and starved condition), high survival was obtained in butterflies pre-incubated for 30 days. However, in butterflies pre-incubated for 15 or 45 days, survival rates decreased with time under overwintering conditions. The above results suggest that decreasing survival rates in these two treatments were due to insufficient development of the fat body in the former and termination of diapause in the latter. Therefore, we conclude that this butterfly may need sufficient time to develop its fat body to survive overwintering.
... According to Sharma et al. (2011), the depletion of proteins may be caused by their breakdown for metabolic use, by impaired amino acid incorporation into polypeptide chains, by inhibiting the synthesis of new proteins, or by breaking down these proteins into amino acids, which are then used as an energy source by the compensatory system to combat stress. The decrease in lipid levels may be caused by these oils' impact on the mobilization of lipid stores for the production of energy as a result of stress that has been generated (Canavoso et al. 2001). The decreased concentrations of glucose, glycogen, and trehalose contents could suggest that the glycolysis process was increased to provide more energy in response to the insecticidal stress (Tufail et al. 1994). ...
The seeds and leaves of Cupressus sempervirens essential oils were evaluated against the khapra beetle, Trogoderma granarium at different concentrations. Mortality, repellence activity, adult emergence rate, larvae chemical profile (protein contents and energy reserves), seed germination effect, and grain damage were assessed. The results of phytochemical screening of C. sempervirens leaf and seed demonstrated the presence of saponins, flavonoids, leucoanthocyanins, cat¬echetical tannins, and gallic tannins. We identified eighty-two (82) compounds for leaves and seventy-four (74) for seeds by GC/MS. The major compounds for leaf and seed EOs were α-pinene (33.65% and 26.53%), δ-3-Carene (14.78% and 19.48%) and terpinolene (4.25% and 4.13%), respectively. C. sempervirens exhibited fumigant toxicity and repellent activity as a function the concentrations. C. sempervirens leaves was most potent both in adult emergence (66.94%) and germination rate (99%) compared to seeds oil. Furthermore, the seed and leaf oils significantly reduced seed damage. Finally, the treatments induced an alteration of the biochemical profile via a decrease in energy reserves and protein content. The data obtained suggest that the toxicity of EO by fumigation could be explained by an alteration of insect metabolism via food uptake and digestion.
... To address whether BubR1 regulates energy metabolism in vivo, we used two BubR1-deficient strains of Drosophila BubR1 MI01546 and BubR1 k03113 (Supplementary Figure 1A) to study the functions of BubR1 in carcass fat body, which stored the lipids to generate energy and acted as a crucial sensor linking nutrient status to energy metabolism [47][48][49][50][51][52]. Lipid mobilization, the process releasing fatty acids from fat stores to generate energy, usually occurred during metabolic stresses like starvation [2]. ...
Lipolysis, the key process releasing fat acids to generate energy in adipose tissues, correlates with starvation resistance. Nevertheless, its detail mechanisms remain elusive. BubR1, an essential mitotic regulator, ensures proper chromosome alignment and segregation during mitosis, but its physiological functions are largely unknown. Here, we use Drosophila adult fat body, the major lipid storage organ, to study the functions of BubR1 in lipolysis. We show that both whole body- and fat body-specific BubR1 depletions increase lipid degradation and shorten the lifespan under fasting but not feeding. Relish, the conserved regulator of IMD signaling pathway, acts as the downstream target of BubR1 to control the expression level of Bmm and modulate the lipolysis upon fasting. Thus, our study reveals new functions of BubR1 in starvation-induced lipolysis and provides new insights into the molecular mechanisms of lipolysis mediated by IMD signaling pathway.
... In insects, lipids assimilated by the midgut are transported to other tissues via the spores present in the hemolymph (Canavoso, Jouni, Karnas, Pennington, & Wells, 2001). Lipids are digested in the midgut, where triacylglycerol (TAG), the main lipid component of the diet, is hydrolyzed by TAG lipase into free fatty acids and monoacylglycerol (Arrese & Soulages, 2010). ...
Cotesia flavipes parasitizes Diatraea saccharalis, a pest that causes major losses to sugarcane production. The mass production of C. flavipes and its subsequent release onto sugarcane is one form of biological control of D. saccharalis. An essential factor for successfully fighting this pest is the development of host diets that can increase the efficiency of C. flavipes production. Palm oil contains saturated fatty acids, unsaturated fatty acids, and polyunsaturated linoleic acid. However, little is known about the effects of palm oil on C. flavipes production in the laboratory. Different concentrations of palm oil were added to the D. saccharalis diet and its nutritional indices were analyzed. Subsequently, the production and sex ratio of C. flavipes were determined. Our results indicated that the addition of higher palm oil concentrations to an artificial diet generated a high relative consumption rate (RCR) in D. saccharalis, and consequently a high relative metabolic rate (RMR), which resulted in a lower production of the parasitoid. In contrast, the lowest palm oil concentration in the artificial diet generated a low RMR and resulted in high-efficiency conversion of ingested food (ECI), enabling D. saccharalis to yield more C. flavipes. This suggests that palm oil influences the quantity of D. saccharalis ingested, which determines the number of C. flavipes that will be generated. In this study, supplementation of a D. saccharalis diet with 0.25% palm oil increased the production of C. flavipes. Therefore, this level of palm oil supplementation can aid in the production of C. flavipes on a laboratory-scale. Further research, including increasing the number of parasitoids, must be performed to mass-produce the augmentative releases of C. flavipes to manage D. saccharalis.
... Statistical differences were determined using two-way ANOVA (****p < 0.0001). The fat body is a secretory and energy storage organ with multiple metabolic functions, including promoting lipid metabolism and ensuring energy for the insect to develop, move and reproduce, by preserving its homeostasis (Arrese & Soulages, 2010;Assis et al., 2014;Canavoso et al., 2001;Roma et al., 2010). Reports in the literature have shown that bmm is highly expressed in this organ in D. melanogaster (Grönke et al., 2005), Bombyx mori (Wang et al., 2010), Glossina morsitans (Attardo et al., 2012), and N. lugens . ...
Lipid storage in the form of triacylglycerol (TAG) is essential for insect life, as it enables flight, development, and reproduction. The activity of the lipase brummer (bmm) has been shown to be essential to insects' homeostasis. The objective of this study was to evaluate how bmm expression occurs in Aedes aegypti larvae and adults, and to observe TAG levels during fasting in adult females. The bmm sequence was identified in A. aegypti and exhibited a patatin-like phospholipase domain reinforced by the presence of a catalytic dyad with serine and aspartate residues, revealing a high degree of similarity with other organisms. Bmm expression was differentiated in the larvae and adult fat body (FB) following TAG reserve dynamics. Bmm was expressed three times in larval stages L3, L4, and pupae compared with L1 and L2, which could indicate its role in the maturation of these insects. In the post-emergence (PE) and post-blood meal (PBM) FB of adult insects, bmm expression varied over several days. PE adults showed a pronounced bmm increase from the third day onward compared with those not subjected to fasting. This was accompanied by a decrease in TAG from the third day Arch Insect Biochem Physiol. 2024;115:e22084. wileyonlinelibrary.com/journal/arch onward, suggesting the participation of bmm. Six hours after blood feeding, TAG levels increased in mosquitos reared in the absence of sucrose, suggesting lipid accumulation to guarantee reproduction. Bmm responded positively to fasting, followed by TAG mobilization in adult FB. During the previtellogenic period, bmm levels responded to low TAG levels, unlike the PBM period. K E Y W O R D S fat body, larvae, lipid storage Highlights • Brummer lipase has been identified in the genome of Aedes aegypti. • Bmm lipase is important for regulating the fasting response during the previtellogenic period.
... Lipids are long-term reserves used when carbohydrates and glycogen are insufficient (Arrese & Soulages, 2010;Klowden 2002). In insects during periods of intense physical activity, such as long-distance flights or courtship and parental care, lipids stored mainly as triglycerides are converted to diglycerides through the synthesis of the adipokinetic hormone secreted during long periods of physical activity (Canavoso et al., 2001). A higher rate of lipid degradation has been reported in insects that perform an intense muscular activity. ...
Parental investment is any expenditure of time or energy by parents that increases their offspring survival at the cost of future reproduction. The costs associated with parental investment can be reflected in a deterioration of their physiological condition. In insects, juvenile hormone has been identified as having a role in the control of parental care. However, its effects on parental investment remain unclear for many taxa, especially in species with exclusive paternal care. We evaluated whether juvenile hormone influences postzygotic parental investment in Abedus ovatus , a waterbug with exclusive paternal care. Males provide parental care by carrying eggs on their backs and ventilating them by generating water currents through push‐ups called brood pumping. In an experiment, we applied methoprene (an analog of juvenile hormone) to males at early and late parental care stages and quantified the frequency of brood pumping and the contents of energy reserves (lipids, carbohydrates, and glycogen) at the end of parental care as a measure of physiological condition. We found that methoprene increases the frequency of brood pumping only when the water temperature increases. However, there was no correlation between the parent's energy reserves and methoprene treatments. We found that males who cared for large egg pads had lower amounts of lipids and carbohydrates at the end of parental care, and both effects are greater as the water temperature increases. These results suggest that energy expenditure during parental care is high due to intense muscular activity during brood pumping, which depletes male energy reserves and could affect future reproduction.
... The midgut of YML releases the digestive enzyme lipase, which breaks down dietary fat into fatty acids and glycerol [93]. Insects do not have bile salts and have developed other strategies to facilitate lipid digestion [94]. In insects, triacylglycerol lipase may generally hydrolyze 2-monoacylglycerol after displacement from the fatty acid into the 1 position, which is favored by the alkaline midgut pH [95]. ...
Yellow mealworm larvae (YML; Tenebrio molitor ) are considered as a valuable insect species for animal feed due to their high nutritional values and ability to grow under different substrates and rearing conditions. Advances in the understanding of entomophagy and animal nutrition over the past decades have propelled research areas toward testing multiple aspects of YML to exploit them better as animal feed sources. This review aims to summarize various approaches that could be exploited to maximize the nutritional values of YML as an animal feed ingredient. In addition, YML has the potential to be used as an antimicrobial or bioactive agent to improve animal health and immune function in production animals. The dynamics of the nutritional profile of YML can be influenced by multiple factors and should be taken into account when attempting to optimize the nutrient contents of YML as an animal feed ingredient. Specifically, the use of novel land-based and aquatic feeding resources, probiotics, and the exploitation of larval gut microbiomes as novel strategies can assist to maximize the nutritional potential of YML. Selection of relevant feed supplies, optimization of ambient conditions, the introduction of novel genetic selection procedures, and implementation of effective post-harvest processing may be required in the future to commercialize mealworm production. Furthermore, the use of appropriate agricultural practices and technological improvements within the mealworm production sector should be aimed at achieving both economic and environmental sustainability. The issues highlighted in this review could pave the way for future approaches to improve the nutritional value of YML.
... Consequently, lipid transport is a pivotal aspect of this metabolism that enables the proper intake and distribution of lipids for their further metabolic processing and cellular incorporation. The study of lipids transport in crustacea was inspired by studying the caterpillar Manduca sexta as a model (Canavoso et al., 2001;Kanost et al., 1990;Law et al., 1992). Particularly, the exchangeable apoLp-III protein, an arthropod lipid transport (Weers and Ryan, 2006). ...
... At 12 h, most DEGs were upregulated and enriched pathways involved in fatty acid metabolism, fatty acid biosynthesis, AMPK signaling pathway, insulin signaling pathway, and acyltransferase activity. Fatty acids are essential for energy storage and release, cell membrane assembly, and the production of signaling molecules in insects (Canavoso et al., 2001;Arrese and Soulages, 2010). The insulin signaling pathway assumes a crucial role in sustaining energy homeostasis through regulating carbohydrate, lipid, protein, and energy metabolism in insects (Wu and Brown, 2006;Géminard et al., 2009;Nässel and Broeck, 2016), which promotes glucose uptake and glycolysis, stimulates lipogenesis, and suppresses lipolysis and gluconeogenesis (Broughton et al., 2005). ...
The eusocial pest, red imported fire ant (Solenopsis invicta), is a highly invasive species that poses significant threats to public safety, agriculture, and the ecological environment. Cycloxaprid, a newly identified effective, slow-acting, and non-repellent insecticide against S. invicta, allows contaminated individuals to transfer the insecticide among nestmates through body contact. However, the molecular-level changes occurring in S. invicta post cycloxaprid exposure and any molecular alterations contributing to the slow demise or decreased sensitivity remain unclear. In this study, transcriptomic and metabolomic techniques were used to investigate the molecular mechanisms of S. invicta exposed to cycloxaprid. Differential analysis results revealed 275, 323, and 536 differentially expressed genes at 12, 24, and 48 h, respectively. Genes involved in lipid and energy metabolism, DNA integration, and hormone synthesis were largely upregulated at 12 h, suggesting S. invicta might actively resist cycloxaprid impacts, and predominantly downregulated at 48 h, indicating further functional impairment and impending death. Also, we observed an imbalance in olfactory perception pathways at 12 h, which may indicate a disruption in the olfactory system of S. invicta. Metabolomic results showed that the regulation of most differential metabolites (DMs) was consistent with the expression changes of their related DEGs at different time points. Our study provides insights into the mechanism underlying slow-acting and non-repellent properties of cycloxaprid against S. invicta. KEYWORDS eusocial insect, formicidae, red imported fire ant, neonicotinoid insecticide, cycloxaprid (2023), Transcriptome and metabolome comprehensive analysis reveal the molecular basis of slow-action and non-repellency of cycloxaprid against an eusocial pest, Solenopsis invicta.
... Phospholipase A1 hydrolyzes the fatty acid from position 1 of the phosphatide, phospholipase A2, from position 2 and, finally, phospholipase B, from both positions (see Fig.2.3). The phosphatide depleted of one acyl ester becomes a lysophosphatide, which have detergent properties (Canavoso et al., 2001). It should be noticed that phospholipase A2 are found among insects, but belongs to a family different from the other lipases (Stanley, 2006) and will not be treated here. ...
Procedures to obtain reliable enzyme kinetic parameters are discussed. The classification of enzymes regarding their function (substrate specificity and mechanism, Enzyme Commission Nomenclature) and protein families (MEROPS, CAZy, and Brenda platforms) is presented. The mechanism of the enzymes acting on the major nutrient substrates is described. The substrates discussed are carbohydrates (starch, oligosaccharides, and disaccharides); peptides (proteins, oligopeptides, and dipeptides); and acylglycerol esters (triacylglycerols and phospholipids). The enzymes discussed in detail are: serine endopeptidases (trypsins, chymotrypsins, elastases); collagenases; carboxypeptidases; aminopeptidases; amylases; α-glucosidases; β-glucosidases; β-fructosidases; β-N-acetylhexosaminidases; α-mannosidases; α-galactosidases; myrosinases; trehalases; triacylglycerol lipases; and phospholipases. Lysosomal proteins recruited as digestive enzymes (cysteine- and aspartic-endopeptidases) and enzymes involved in the degradation of cell walls are the subject of specific chapters.
... It also indicates that TGs may be less important for the CNS in both classes. However, it is not clear whether the supply of FAs is controlled in the same way in bees as it is in other animal clades (reviews of FA metabolism in bees, Arrese et al., 2001;Canavoso et al., 2001;Majerowicz & Gondim, 2013). For example, which FAs are produced or modified endogenously, and where, by bees has not yet been fully mapped. ...
Background
Bees provide essential pollination services for many food crops and are critical in supporting wild plant diversity. However, the dietary landscape of pollen food sources for social and solitary bees has changed because of agricultural intensification and habitat loss. For this reason, understanding the basic nutrient metabolism and meeting the nutritional needs of bees is becoming an urgent requirement for agriculture and conservation. We know that pollen is the principal source of dietary fat and sterols for pollinators, but a precise understanding of what the essential nutrients are and how much is needed is not yet clear. Sterols are key for producing the hormones that control development and may be present in cell membranes, where fatty-acid-containing species are important structural and signalling molecules (phospholipids) or to supply, store and distribute energy (glycerides).
Aim of the review
In this critical review, we examine the current general understanding of sterol and lipid metabolism of social and solitary bees from a variety of literature sources and discuss implications for bee health.
Key scientific concepts of review
We found that while eusocial bees are resilient to some dietary variation in sterol supply the scope for this is limited. The evidence of both de novo lipogenesis and a dietary need for particular fatty acids (FAs) shows that FA metabolism in insects is analogous to mammals but with distinct features. Bees rely on their dietary intake for essential sterols and lipids in a way that is dependent upon pollen availability.
... In our study, the total fatty acids varied among the four hemp varieties and ranged rather low in comparison, from 0.438% in Joey to 0.537% in Henola (Table 3). Linoleic and linolenic acids (polyunsaturated fatty acids), oleic (monosaturated fatty acid), and palmitic (saturated fatty acids) are all components reported to satisfy the nutritional needs of bees and other pollinators [86][87][88][89][90][91]. Linoleic and linolenic acids were higher in Joey, the variety that recorded the highest number of bees while palmitic and oleic acids were higher in Henola which had the second highest. ...
Apart from its economic value, industrial hemp (Cannabis sativa L.) is a prolific pollen producer, serving as a food source for bees. However, little is known regarding the extent to which varietal differences in hemp pollen chemistry influences bee preference. Here, we report the chemical profile of pollen from four hemp varieties (Canda, CFX-2, Henola, and Joey) and bee abundance and diversity, using direct visual counts and pan traps. The number and type of bees on each variety was recorded and the chemical composition (proximate analysis and mineral, amino, and fatty acid profiles) of pollen from each hemp variety was determined. During the entire sampling period, three bee types (bumble bees, honey bees, and sweat bees) were recorded, with a combined total of 1826. Among these, sweat bees and bumble bees were the most prevalent and were highest on the Joey variety. The four varieties expressed protein content ranging from 6.05% to 6.89% and the highest in Henola. Seventeen amino acids were expressed in all varieties, with leucine recording the highest content ranging from 4.00 mg/g in Canda to 4.54 mg/g in Henola. In general, Henola expressed high protein, amino acid, and saturated and monosaturated fatty acid contents and recorded significantly fewer bees compared with Joey, which had a low content of these components and a high content of polyunsaturated fatty acids. Our findings suggest that, while industrial hemp offers abundant and accessible pollen that would promote bee health and sustainability of their ecosystem services, the nutritional quality may not be adequate for bee growth and development as an exclusive pollen source.
... Furthermore, it is well known that an early step in the mobilisation of fat reserves, is the activity of triacylglycerol lipases that hydrolase TGs from the fat body (Arrese & Soulages, 2010;Skowronek et al., 2021). which through β-oxidation, supply energy in the absence of sufficient carbohydrate and protein resources (Arrese & Soulages, 2010;Canavoso et al., 2001). Our main results showed an increase of unsaturated TGs in the fat body of newly emerged honey bees during starvation, while saturated TGs decreased in abundance. ...
Honey bee nutritional health depends on nectar and pollen, which provide the main source of carbohydrates, proteins and lipids to individual bees. During malnutrition, insect metabolism accesses fat body reserves. However, this process in bees and its repercussions at the colony level are poorly understood. Using untargeted lipidomics and gene expression analysis, we examined the effects of different feeding treatments (starvation, sugar feeding and sugar + pollen feeding) on bees and correlated them with colony health indicators. We found that nutritional stress led to an increase in unsaturated triacylglycerols and diacylglycerols, as well as a decrease in free fatty acids in the bee fat body. Here, we hypothesise that stored lipids are made available through a process where unsaturations change lipid's structure. Increased gene expression of three lipid desaturases in response to malnutrition supports this hypothesis, as these desaturases may be involved in releasing fatty acyl chains for lipolysis. Although nutritional stress was evident in starving and sugar-fed bees at the colony and physiological level, only starved colonies presented long-term effects in honey production.
... We found that some diacylglycerols are more common in queen food than in king food. In insects, diacylglycerol in the diet is absorbed from the midgut lumen (35,36), consistent with our observation that the midgut of queens is significantly larger than in other castes (Fig. 4). Lipidomic studies of the higher termite Macrotermes natalensis showed that the amount of diacylglycerol in queens' fat bodies increases during reproductive development (37). ...
Society in eusocial insects is based on the reproductive division of labor, with a small number of reproductive individuals supported by a large number of non-reproductive individuals. Because inclusive fitness of all colony members depends on the survival and fertility of reproductive members, sterile members provide royals with special treatment. Here we show that termite kings and queens each receive special food of a different composition from workers. Sequential analysis of feeding processes demonstrated that workers exhibit discriminative trophallaxis, indicating their decision-making capacity in allocating food to the kings and queens. LC-MS/MS analyses of the stomodeal food and midgut contents revealed king- and queen-specific compounds including diacylglycerols and short-chain peptides. DESI-MSI analyses of ¹³C-labelled termites identified phosphatidylinositol and acetyl-L-carnitine in the royal food. Comparison of the digestive tract structure showed remarkable differences in the volume ratio of the midgut-to-hindgut among castes, indicating that digestive division of labor underlies reproductive division of labor. Our demonstration of king- and queen-specific food in termites provides insight into the nutritional system that underpins the extraordinary reproduction and longevity of royals in eusocial insects.
... Some FAs (e.g., linoleic and linolenic acid) are essential for insects and therefore need to be consumed in sufficient amounts and appropriate ratios [80]. In turn, excess concentrations of FAs in the hemolymph can lead to cell membrane damage [81] and subsequently reduced survival or reproduction, as shown in bumble bees [3] and honeybees [82]. In consequence, insects should be able to assess the fat content of food to some degree, either in detail or at least by assessing overall lipid amounts depending on species-specific ecological niche requirements (Figure 1). ...
Insects are equipped with neurological, physiological, and behavioral tools to locate potential food sources and assess their nutritional quality based on volatile and chemotactile cues. We summarize current knowledge on insect taste perception and the different modalities of reception and perception. We suggest that the neurophysiological mechanisms of reception and perception are closely linked to the species-specific ecology of different insects. Understanding these links consequently requires a multidisciplinary approach. We also highlight existing knowledge gaps, especially in terms of the exact ligands of receptors, and provide evidence for a perceptional hierarchy suggesting that insects have adapted their reception and perception to preferentially perceive nutrient stimuli that are important for their fitness.
... Lipids, as well as proteins, is important for the development of bee colonies. According to CANAVOSO et al. (2001), lipids are involved in production of cuticular hydrocarbons and wax, behavioral maturation in adults, diapause, learning, and development of glands that produce food for the offspring. The bee pollen samples analyzed in the present study showed significantly lower lipid amounts (0.49 to 4.70%) than those found by MARTINS et al. (2011) for bee pollen from different regions of the country (4.01 to 13.32%). ...
The objective of this work was to characterize nutritional parameters of bee pollens from plant species occurring in a semiarid region, in Picos, state of Piaui, Brazil. Bee pollen samples were collected from the experimental apiary of the Study Group on Bees from the Semiarid Region of Piaui (GEASPI/UFPI) and subjected to melissopalynological analysis to determine their botanical origins, and bromatological analysis (crude protein, lipids, fibers, and ash) in the Laboratory of Animal Nutrition of the Department of Zootechnics of the Federal University of Piaui (UFPI), in Teresina, Piaui (DZO/UFPI/Teresina). Six plant species (Aspilia sp., Senna obtusifolia,Mimosa pudica L., Cupheaericoides, Croton sp., and Mimosa caesalpiniifolia) were predominant for bee pollen production in the study area. Therefore, the nutritional compositions of the pollen produced in the Caatinga area varied according to their botanical origin, as shown by the crude protein (20.75% to 38.18%), fiber (0.53% to 1.37%), lipid (0.49% to 4.7%), and total mineral (2.56 to 4.17%) contents. Bromatological parameters also varied according to the botanical origin of the pollens evaluated. The study region has considerable diversity of pollinator plant species that provide bee pollens with a wide spectrum of nutritional characteristics.
... One physiological trait that could track seasonal changes in temperature is lipid content. Fat bodies are metabolically active tissues that are important for storing and releasing energy in response to demand (Canavoso et al. 2001, Arrese and Soulages 2010, Sinclair and Marshall 2018. To survive high and low temperatures, insects must often mobilize energy stores, such as lipids, to fuel cellular responses. ...
Temperature is one of the most important environmental conditions affecting physiological processes in ec-tothermic organisms like ants. Yet, we often lack information on how certain physiological traits covary with temperature across time. Here, we test predictions on how one trait-lipid content-covaries with temperature using a conspicuous, ground-dwelling harvester ant. We focus on lipid content as fat bodies are metabolically active tissues that are important for storing and releasing energy in response to demand, which could be vital for survival under variable temperatures. From March to November, we extracted lipids from surface workers of 14 colonies while simultaneously recording ground temperature. We first assessed if lipid content was highest during cooler temperatures when ants were less active and less metabolically stressed. In doing so, we found that lipid content of ants declined almost 70% from cool months (November lipid content = 14.6%) to hot months (August lipid content = 4.6%). We next assessed if lipid levels from a group of ants collected at a single time point could change by placing individuals into environmental chambers set at 10, 20, and 30°C (i.e., the approximate span of average temperatures from March to November). Temperature again had a significant impact such that after 10 days, lipid content of ants in the hottest chamber (30°C) had decreased by more than 75%. While intraspecific variation in physiological traits often follows seasonal patterns, our results suggest fluctuations in temperature may account for a portion of the variance observed in traits like lipid content.
... Our data corroborate with those obtained by the treatment of Culex pipiens larvae with Ocimum basilicum (47) and Thymus vulgaris (15) (49) have reported a decrease in the total lipid content in Culex pipiens mosquito treated with Rosmarinus officinalis and Petroselinum crispum essential oils respectively. The decline of lipid levels might be due to the effects of these oils on the mobilization of lipid reserves for energy production as a result of induced stress (61). Reduction of lipid levels in the larvae treated with plant essential oils may be due to their effects on the lipid metabolism, and use of lipid reserves for energy generation as a result of induced stress (62). ...
This study was done to determine the chemical composition of essential oil of Eucalyptus globulus (Labill.) (Myrtaceae) leaves cultivated in Tebessa (Algeria) and to assess their potential larvicidal activity against the most abundant mosquito specie, Culiseta longiareolata (M., 1838) (Diptera, Culicidae). Under standard laboratory conditions the larvicidal activity of essential oil extracted from E. globulus was tested at 6-concentrations (0,5,10,20,30 and 40 ppm) on newly molted fourth-instar Culiseta longiareolata larvae. The effects were examined on the mortality, morphometric measurements and biochemical composition of larvae, pupae and adults body. The steam distillation of E. globulus dry flowers yielded 2.89 + 0.64 % essential oil. Its chemical composition by GC/MS, identified compounds. The major compounds were : Sabinene (35.38 %) and α-Phellandrene (12.64 %). Bioassay test revealed that E. globulus essential oil exhibited larvicidal activity against fourth instar larvae of C. longiareolata at 24 h (LC50 and LC90 values were 24.23 and 46.13 ppm, respectively). The morphometric study showed that the essential oil decreased the growth of different developmental stages of C. longiareolata. Moreover, it reduced significantly the body contents of carbohydrates and lipids in larvae, pupae, adult male and female and increased the protein content. Due to its mosquitocidal efficacy, E. globulus essential oil may be used as an attractive candidate for further study to monitor resistance of mosquito vectors.
... Lipids remain one of the most important energy reserves in most diapausing insects because of their caloric content, low hydration state, and perhaps relatively high yield of metabolic water. They are obtained from food or synthesized from carbohydrates and amino acid precursors via the tricarboxylic acid cycle intermediate (Canavoso et al., 2001). Their storage has been an important factor in mitigating the metabolic challenges of diapause (Hahn and Denlinger, 2007). ...
Diapause is a complex life history strategy aimed at tolerating or circumventing stress in insects. It is accompanied by alterations in the food reserve levels to cope with the energy demand of this life stage. In the pallid emperor moth (Cirina forda), little is known about the patterns of accumulation and utilization of food reserves before and during diapause, respectively. The accumulation and utilization of food reserves in the haemolymph and the whole body of diapause-destined larvae and diapausing pupae of Cirina forda were progressively compared using photometry and HPLC. The quantity of glucose, total carbohydrate, fats, protein, and amino acids measured were taken as indices of food reserve accumulation and utilization by the immature stages of the insect in this study. Data collated were analyzed using Analysis of Variance (ANOVA), and the means were separated using Fisher's Least Significance Difference (LSD). The results showed progressive accumulation of glucose from 46.20 to 105.06 mg/100 g, total carbohydrates from 175.39 to 212.54 mg/100 g, lipids from 440.49 to 641.57 mg/100 g, and protein from 306.04 to 378.83 mg/100 g in the haemolymph of diapause-destined larvae. The reserves decreased progressively (72.1%, 60.3%, 5.7%, and 6.9%) in diapausing pupae. Total amino acids increased by 2.8%, while 61.1% of amino acids in the whole pupae increased significantly (P<0.05). The study concluded that C. forda accumulates food reserves in preparation for diapause, and reserves decline as they are probably utilized during diapause development.
... High dietary lipids have frequently been shown to have detrimental health effects on insect survival, including inManduca sexta larva[54], B. terrestris workers[30], and golden-haired blowfly Calliphora stygia adults[55]. A previous study on lipid metabolism in insects showed that high dietary lipid amounts may not be taken up quickly enough by midgut cells, resulting in the presence of toxic levels[30,56]. In addition, diets rich in polyunsaturated fatty acids (PUFAS), which are the dominant fatty acid in pollen, can increase the risk of lipid peroxidation in cellular membranes and ultimately reduce survival[57]. ...
Most pollination services are provided by annual bees that go through a winter diapause, during which they are exposed to extreme temperatures, pathogens, and starvation. The ability of bees to successfully face these stressors during diapause and subsequently initiate a nest depends on their overall nutritional state and an adequate preparatory diet.
Here, we used queens of the common eastern bumble bee, Bombus impatiens, to examine how pollen diets varying in their protein to lipid ratio and total nutrient amounts affected queen performance during and after diapause. We compared diapause survival and reproductive performance post diapause across different diets and found that queen survival was highest when pollen had a nutritional ratio of approximately 5:1 (protein to lipid). This diet is significantly enriched in proteins compared to the pollen fed to bumble bees in the lab (1:1) or commonly available in agricultural landscapes. Altering the quantity of macronutrients within this ratio did not improve survival or performance. Our results emphasize the importance of adequate nutrition for diapause performance in bees with annual life cycles and the importance of providing annual bees with floral provisioning based on their individual nutritional targets.
... For example, 24-methylenecholesterol, β-sitosterol, and δ5-avenasterol affect the size and growth rate of bumble bee larvae (Vanderplanck et al., 2014). However, insects are generally unable to synthesize sterols de novo (Svoboda et al., 1978;Canavoso et al., 2001) and therefore require external sources for their sterol supply. Especially for herbivorous insects, the variation in dietary sterol type and ratio are of vital importance (Behmer, 2017). ...
Premise:
Many flowering plants depend on insects for pollination and thus attract pollinators by offering rewards, mostly nectar and pollen. Bee pollinators rely on pollen as their main nutrient source. Pollen provides all essential micro- and macronutrients including substances that cannot be synthesized by bees themselves, such as sterols, which bees need for processes such as hormone production. Variations in sterol concentrations may consequently affect bee health and reproductive fitness. We therefore hypothesized that (1) these variations in pollen sterols affect longevity and reproduction in bumble bees and (2) can thus be perceived via the bees' antennae before consumption.
Methods:
We studied the effect of sterols on longevity and reproduction of Bombus terrestris workers in feeding experiments and investigated sterol perception using chemotactile proboscis extension response (PER) conditioning.
Results:
Workers could perceive several sterols (cholesterol, cholestenone, desmosterol, stigmasterol, β-sitosterol) via their antennae but not differentiate between them. However, when sterols were presented in pollen, and not as a single compound, the bees were unable to differentiate between pollen differing in sterol content. Additionally, different sterol concentrations in pollen neither affected pollen consumption nor brood development or worker longevity.
Conclusions:
Since we used both natural concentrations and concentrations higher than those found in pollen, our results indicate that bumble bees may not need to pay specific attention to pollen sterol content beyond a specific threshold. Naturally encountered concentrations might fully support their sterol requirements and higher concentrations do not seem to have negative effects.
... Except for de novo synthesis, the transport of dietary lipids is another important process for TG formation in the fat body. After being digested by lipase in the intestine, dietary lipids are absorbed by enterocytes and packaged into lipoprotein particles by lipoprotein Lipophorin (Lpp) [17,18]. Lpp is produced in the fat body and functions as the major hemolymph lipid carrier to transport lipids into the fat body for synthesizing TG [18]. ...
Lipid homeostasis is essential for insect growth and development. The complex of proteins associated with Set 1 (COMPASS)-catalyzed Histone 3 lysine 4 trimethylation (H3K4me3) epigenetically activates gene transcription and is involved in various biological processes, but the role and molecular mechanism of H3K4me3 modification in lipid homeostasis remains largely unknown. In the present study, we showed in Drosophila that fat body-specific knockdown of will die slowly (Wds) as one of the COMPASS complex components caused a decrease in lipid droplet (LD) size and triglyceride (TG) levels. Mechanistically, Wds-mediated H3K4me3 modification in the fat body targeted several lipogenic genes involved in lipid synthesis and the Lpp gene associated with lipid transport to promote their expressions; the transcription factor heat shock factor (Hsf) could interact with Wds to modulate H3K4me3 modification within the promoters of these targets; and fat body-specific knockdown of Hsf phenocopied the effects of Wds knockdown on lipid homeostasis in the fat body. Moreover, fat body-specific knockdown of Wds or Hsf reduced high-fat diet (HFD)-induced oversized LDs and high TG levels. Altogether, our study reveals that Wds-mediated H3K4me3 modification is required for lipid homeostasis during Drosophila development and provides novel insights into the epigenetic regulation of insect lipid metabolism.
... Ae. aegypti and some other Diptera predominantly transport TG via lipophorin, not DG as is the case of most other insects [48][49][50]. Moreover, a general observation for insects is that the midgut can convert DG to TG in the presence of high concentrations of potentially toxic fatty acids; this conversion could maintain low intracellular levels of DG and fatty acids to prevent lipotoxicity [29,51,52]. Additionally, there are other possibilities for lipid movement not based on DG transport, including evolutionarily conserved mechanisms for movement of fatty acids [53]. ...
We conducted a lipidomic analysis of the whole body of female Aedes aegypti mosquitoes at different time points over the course of feeding and reproduction. There were temporal biphasic increases of more than 80% of lipids identified at the time of feeding and from 16 h to 30 h post blood meal (PBM). During these two increases, the abundance of many lipids dropped while body weight remained stable, probably reflecting blood lipid digestion and the synthesis of vitellogenin in this period. A concerted temporal pattern was particularly strong at the second peak for membrane and signalling lipids such as phosphatidylethanolamine (PE), phosphatidylinositol (PI), cardiolipin (CL), hexosylceramide (HexCer) and lyso-phosphatidic acid (LPA). Lyso-glycerophospholipids showed three distinct change patterns that are functionally related: Lyso-PE and Lyso-phosphatidylcholine (LPC), which are membrane lipids, showed little change; LPA, a signalling lipid, showed a significant increase from 16 to 30 h PBM; Lyso-PI, a bioactive lipid, and both lyso-phosphatidylglycerol (LPG) and lyso-phosphatidylserine (LPS), which are bacterial membrane lipids, showed one significant increase from the time of feeding to 16 h post blood meal. The result of our study on the anautogenous insect Ae. aegypti point to specific lipids likely to be important in the reproductive process with a role in the formation and growth of ovarian follicles.
... Also, in this study total lipids were decreased in the treated insect (S. littoralis and A. gossypii). This decrease may be caused by the use of lipids for energy synthesis and metabolic activity to battle the oxidative stress brought on by using synthesized compounds on insects (Canavoso et al., 2001). ...
A novel series of anticipated insecticidal activity 2-pyridone derivatives incorporating a 3,4-(Methylenedioxy) aniline moiety were synthesized in a good yield through interaction of the readily available cyanoacetanilide, N-(benzo[d][1,3] dioxol-5-yl)-2-cyanoacetamide (1) with different arylidene ethyl cyanoacetate and arylidene malononitrile derivatives. The newly synthesized skeletones were elucidated by IR, MS and 1 H NMR spectral techniques. Toxicological and biochemical parameters of the examined compounds (1-5) against the cotton pests, Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae) as well as cotton aphid, Aphis gossypii (Glover) (Hemiptera: Aphididae) under laboratory conditions, were also inspected. As regards the indomitable LC50 values, cyanoacetanilides, 5, 1, 3, 4 and 2, showed proper toxic effects against the 3 rd instar larvae of S. littoralis after 7 days post treatment with LC50 values of 970, 1075, 1088, 1574 and 1996 ppm, respectively, and toxicity index of 100%, 90%, 89%, 61% and 48%, respectively. Otherwise, cyanoacetanilides, 5, 2, 1, 3 and 4, showed a powerful toxicity against A. gossypii after 48 hours post treatment with LC50 values of 50, 58, 81, 103 and 343 ppm, respectively, and toxicity index of 100%, 86%, 61%, 48% and 14%, respectively. As well as, all tested compounds caused significant changes of estimated insect enzymes and total protein and lipids compared with control.
... In this study, we clarify that the digestive enzymes α-amylase and lipase in the midgut are closely related to larval feeding and are regulated by the NPF/NPFR system via the insulin signalling pathway. Insect α-amylase and lipase mainly decompose the respective starch and lipids in foods into reducing sugars and fatty acids [60,61]. When they are inhibited, insect nutrition is impaired, which leads to retarded growth and development and even death [37]. ...
Feeding is crucial for the growth and survival of animals, including humans, but relatively little is known about how it is regulated. Here, we show that larval feeding in Ostrinia furnacalis is regulated by neuropeptide F (NPF, the homologous peptide of mammalian NPY) via the insulin signalling pathway in the midgut. Furthermore, the genes pi3k and mtor in the insulin pathway positively regulate α-amylase and lipase of the midgut by recruiting the transcription factors c-Myc and PPARγ for binding to the promotors of these two enzymes. Importantly, we find that the feeding behaviour and the digestive system of midgut in O. furnacalis larvae are closely related and interactive in that knocking down α-amylase or lipase induces a reduction in larval feeding, while food-deprived larvae lead to fewer expressions of α-amylase and lipase. Importantly, it is the gut NPF that regulates the α-amylase and lipase, while variations of α-amylase and lipase may feed back to the brain NPF. This current study reveals a molecular feedback mechanism between feeding behaviour and the digestive system that is regulated by the conserved NPF via insulin signalling systems in the midgut of O. furnacalis larvae.
Kombucha tea is a traditional beverage originating from China and has recently gained popularity worldwide. Kombucha tea is produced by the fermentation of tea leaves and is characterized by its beneficial properties and varied chemical content produced during the fermentation process, which includes organic acids, amino acids, vitamins, minerals, and other biologically active compounds. Kombucha tea is often consumed as a health drink to combat obesity and inflammation; however, the bioactive effects of kombucha tea have not been thoroughly researched. In this study, we reveal the underlying mechanisms of the beneficial properties of kombucha tea and how they protect against obesity and inflammation by studying Drosophila models. We established an inflammatory Drosophila model by knocking down the lipid storage droplet‐1 gene, a human perilipin‐1 ortholog. In this model, dysfunction of lipid storage droplet‐1 induces inflammation by enhancing the infiltration of hemocytes into adipose tissues, increasing reactive oxygen species production, elevating levels of proinflammatory cytokines, and promoting the differentiation of hemocytes into macrophages. These processes are regulated by the c‐Jun N‐terminal Kinase (JNK) pathway. Using this unique Drosophila model that mimics mammalian inflammation, we verified the beneficial effects of kombucha tea on reducing tissue inflammation. Our data confirms that kombucha tea effectively improves inflammatory conditions by suppressing the expression of cytokines and proinflammatory responses induced by lipid storage droplet‐1 dysfunction. It was found that kombucha tea consumption alleviated the production of reactive oxygen species and activated the JNK signaling pathway, signifying its potential as an anti‐inflammatory agent against systemic inflammatory responses connected to the JNK pathway. Kombucha tea reduced triglyceride accumulation by increasing the activity of Brummer (a lipase), thereby promoting lipolysis in third‐instar larvae. Therefore, kombucha tea could be developed as a novel, functional beverage to protect against obesity and inflammation. Our study also highlights the potential use of this innovative model to evaluate the effects of bioactive compounds derived from natural products.
The Indian meal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae) is an important insect pest on a wide range of stored food diets. This study employed gas-liquid chromatography to investigate the influence of different diets (pistachio, raisins, and walnuts) on the composition of phospholipids and triglycerides in fifth
instar larvae of P. interpunctella. The fatty acid profiles of the larvae revealed seven essential fatty acids including myristic, palmitic, palmitoleic, stearic, oleic, linoleic, and linolenic acids. The fatty acid composition of larvae extracted phospholipids and triglycerides also varied according to the diet type. In terms of phospholipids, the highest concentration of myristic acid was observed in larvae fed walnut. Raisins exhibited the highest levels of palmitoleic and oleic acid, while pistachio demonstrated the highest concentration of linoleic acid. However, no significant differences were observed among the treatments concerning palmitic acid, stearic acid, and linolenic acid. Regarding triglycerides, no significant differences were found among the treatments in terms of myrisitc acid and oleic acid. However, the raisins treatment displayed the highest amount of palmitoleic acid, while both pistachio and walnut treatments exhibited the highest levels of linoleic acid. Additionally, the concentration of linolenic acid in larvae fed walnut was higher than other test diets. These findings provide valuable insights into the fatty acid composition of P. interpunctella fed different diets. Such knowledge can be utilized in developing pest management strategies, as the manipulation of fatty acid profiles in insects’ diet could potentially impact their growth, development, and fitness.
Ticks are ectoparasites that feed on blood and have an impressive ability to consume and process enormous amounts of host blood, allowing extremely long periods of starvation between blood meals. The central role in the parasitic lifestyle of ticks is played by the midgut. This organ efficiently stores and digests ingested blood and serves as the primary interface for the transmission of tick-borne pathogens. In this study, we used a label-free quantitative approach to perform a novel dynamic proteomic analysis of the midgut of Ixodesricinus nymphs, covering their development from unfed to pre-molt stages. We identified 1534 I. ricinus-specific proteins with a relatively low proportion of host proteins. This proteome dataset, which was carefully examined by manual scrutiny, allowed precise annotation of proteins important for blood meal processing and their dynamic changes during nymphal ontogeny. We focused on midgut molecules related to lipid hydrolysis, storage, and transport, opening a yet unexplored avenue for studying lipid metabolism in ticks. Further dynamic profiling of the tick's multi-enzyme digestive network, protease inhibitors, enzymes involved in redox homeostasis and detoxification, antimicrobial peptides, and proteins responsible for midgut colonization by Borrelia spirochetes promises to uncover new targets for targeting tick nymphs, the most critical life stage for transmission the pathogens that cause tick-borne diseases.
Bactrocera dorsalis is a well-known invasive pest that causes considerable ecological and economic losses worldwild. Although it has a wide environmental tolerance, few studies have reported its mechanism of adaptation to multiple sub-lethal environmental stresses. In this study, 38, 41, 39 and 34 metabolites changed significantly in B. dorsalis under four sub-lethal stresses (heat, cold, desiccation and hypoxia), as found by the metabolomic method. Therein, lactic acid and pyruvic acid were induced, whereas metabolites in the tricarboxylic acid (TCA) cycle such as citric acid, α-ketoglutarate acid, malic acid and fumaric acid were reduced under at least one of the stresses. Enzyme activity and quantitative polymerase chain reaction (qPCR) analyses verified the repression of pyruvic acid proceeding into the TCA cycle. In addition, the levels of several cryoprotectants and membrane fatty acids in B. dorsalis were altered. The findings indicated that B. dorsalis has evolved shared metabolic pathways to adapt to heat, hypoxia and desiccation stresses, such as reducing energy consumption by activating the anaerobic glycolytic metabolism. Cryoprotectants and membrane fatty acids were produced to improve the efficiency of stress resistance. This study revealed the unique and generic crossed physiological mechanism of insects to adapt to various environmental stresses.
Background:
The bean bug, Riptortus pedestris, is known to cause significant economic losses in soybean crops due to its seed-sucking behavior, but the mechanism of its adaptation to lipid-rich seeds remains poorly understood. To exploit potential target genes for controlling this pest, neutral lipases are functionally characterized in this study.
Results:
In this study, a total of 69 lipases are identified in R. pedestris, including 35 neutral lipases that underwent significant expansion. The phylogeny, expression patterns, and catalytic capacity of neutral lipases were investigated and we select 6 salivary gland-specific, 8 gut-specific, and 3 ovary-specific genes for functional analysis. All three ovary-specific neutral lipases (Chr1.3195, Chr1.0994, and Chr5.0087) are critical for insect reproduction, while a few gut-specific neutral lipases (Chr4.0221 and Chr1.3207) influence insect survivorship or weight gain. In contrast, no significant phenotype change is observed when silencing salivary gland-specific neutral lipases.
Conclusion:
The Chr1.3195, Chr1.0994, Chr5.0087, Chr4.0221, and Chr1.3207 are essential for R. pedestris feeding and reproduction, and the insect is highly sensitive to their deficiency, suggesting that neutral lipases are promising candidates for application in RNAi-based control of this destructive pest. This article is protected by copyright. All rights reserved.
Among many medically important pathogens, arboviruses like dengue, Zika and chikungunya cause severe health and economic burdens especially in developing countries. These viruses are primarily vectored by mosquitoes. Having surmounted geographical barriers and threat of control strategies, these vectors continue to conquer many areas of the globe exposing more than half of the world’s population to these viruses. Unfortunately, no medical interventions have been capable so far to produce successful vaccines or antivirals against many of these viruses. Thus, vector control remains the fundamental strategy to prevent disease transmission. The long-established understanding regarding the replication of these viruses is that they reshape both human and mosquito host cellular membranes upon infection for their replicative benefit. This leads to or is a result of significant alterations in lipid metabolism. Metabolism involves complex chemical reactions in the body that are essential for general physiological functions and survival of an organism. Finely tuned metabolic homeostases are maintained in healthy organisms. However, a simple stimulus like a viral infection can alter this homeostatic landscape driving considerable phenotypic change. Better comprehension of these mechanisms can serve as innovative control strategies against these vectors and viruses. Here, we review the metabolic basis of fundamental mosquito biology and virus-vector interactions. The cited work provides compelling evidence that targeting metabolism can be a paradigm shift and provide potent tools for vector control as well as tools to answer many unresolved questions and gaps in the field of arbovirology.
The concentration-mortality response of third instar larvae of Chrysomya megacephala (Diptera: Calliphoridae) to a synthetic insecticide, imidacloprid, and its impact on histopathological, histochemical, and biochemical parameters were determined in laboratory assays. Larvae displayed a concentration and time-dependent mortality response for the insecticide. Histopathological studies exhibited quite noticeable modifications in the epithelial cells, peritrophic membrane, basement membrane and muscular layer of the larval midgut. The ultrastructural analysis demonstrated alterations in nuclei, lipid spheres, microvilli, mitochondria, rough endoplasmic reticulum and lysosomes. In addition, histochemical tests on the midgut were performed, which revealed a strong reaction for proteins and carbohydrates in the control group and a weak reaction in the group exposed to imidacloprid in a dose and time-dependent manner. Imidacloprid also caused a significant reduction in the total midgut content of carbohydrates, proteins, lipids and cholesterol. Larvae treated with imidacloprid also showed a reduction in the activities of acid and alkaline phosphatases at all concentrations compared to untreated larvae.
Lipophagy, the process of selective catabolism of lipid droplets (LDs) by autophagy, maintains lipid homeostasis and provides cellular energy under metabolic adaptation, yet its underlying mechanism remains largely ambiguous. Here, we show that the Bub1-Bub3 complex, the crucial regulator involved in the whole process of chromosome alignment and separation during mitosis, controls the fasting-induced lipid catabolism in the fat body (FB) of Drosophila. Bidirectional deviations of the Bub1 or Bub3 level affect the consumption of triacylglycerol (TAG) of fat bodies and the survival rate of adult flies under starving. Moreover, Bub1 and Bub3 work together to attenuate lipid degradation via macrolipophagy upon fasting. Thus, we uncover physiological roles of the Bub1-Bub3 complex on metabolic adaptation and lipid metabolism beyond their canonical mitotic functions, providing insights into the in vivo functions and molecular mechanisms of macrolipophagy during nutrient deprivation.
Insect species that are nectivorous as adults acquire essential fatty acids almost exclusively from host plants during larval development. Thus, as essential fatty acids are important for a number of different biological processes, adult allocation of this limited resource may result in important trade-offs. Most lepidopteran species that migrate do so as sexually immature adults, so essential fatty acids used for migratory flight would not be available for subsequent reproduction. Using the true armyworm, Mythimna unipuncta, as a model system we analyzed fat body samples to test the hypothesis that environmental cues would influence the use of essential fatty acids during migratory flight. We used diets manipulated isotopically to trace origins and use of stored lipids and used chromatographic analyses to determine fatty acid composition. In the first experiments, 5-day old moths that had been reared in summer or fall (migratory) conditions and were force flown for different lengths of time (0–6 h) after which samples of the fat body were analyzed. Rearing conditions did not affect fatty acid loading however patterns of use during flight differed with essential fatty acids being conserved under fall but not summer conditions. As migratory flight can take several days, we repeated the experiment when 5-day old moths were flown for 8 h each day for up to 5 days. Some moths were provided access to sugar water after each flight while others were only given water or only given sugar water once. When sugar water was readily or sporadically available, moths reared under fall conditions conserved their essential fatty acids indicating that the environmental cues responsible for the onset of migratory flight result in physiological changes that modify lipid use. However, when moths had only water, the essential fatty acids were not conserved, highlighting the importance of nectar availability at stopovers for the conservation essential fatty acids during migration. Isotopic analysis of the moth fat body indicated a large contribution of adult-derived diet to lipids used as fuel. The implications of using isotopic approaches to other flight studies and future research on differential resource allocation in winged monomorphic migratory insects are discussed. Summary statement: Isotopic tracing methods and gas chromatography were used to demonstrate that environmental cues can impact patterns of fatty acid use in true armyworm moths. In particular, essential fatty acids are conserved during migratory flight. However, availability of adult food sources will determine the degree to which essential fatty acids are conserved.
Haemolymph plays an important role in the physiology of insect's life like transportation of nutrients, hormones and metabolic waste and the main function as acting against disease pathogens. Haemolymph contain many antimicrobial peptides which, act against invading pathogens and their proteins were found to involve in humoral mediated immune response. Silkworm Bombyx mori the model animal was used in this experiment to find out the biochemical changes in relation to wound healing. The 4 th day of 5 th instar larva was wounded and the haemolymph was collected during 2, 4, 6, 8, 12, 16, 24 and 48 hours and subjected to biochemical analysis like protein, carbohydrate and lipid. The haemolymph proteins decreased gradually and a statistically significant rise was noted, but decreased (p<0.05) during 48 hr after wounding. A significant increase in the lipid content was observed in all the wounded groups. Carbohydrate concentration also enhanced in all the wounded groups irrespective of the time. Suggest production of more biochemicals for the survival or precursor for the production of anti-pathogenic compounds. All the three parameters was found to decrease significantly irrespective of time.
Rhodnius prolixus is a hemimetabolous, hematophagous insect, and both nymphs and adults feed exclusively on blood. The blood feeding triggers the molting process and, after five nymphal instar stages, the insect reaches the winged adult form. After the final ecdysis, the young adult still has a lot of blood in the midgut and, thus, we have investigated the changes in protein and lipid contents that are observed in the insect organs as digestion continues after molting. Total midgut protein content decreased during the days after the ecdysis, and digestion was finished fifteen days later. Simultaneously, proteins and triacylglycerols present in the fat body were mobilized, and their contents decreased, whereas they increased in both the ovary and the flight muscle. In order to evaluate the activity of de novo lipogenesis of each organ, the fat body, ovary and flight muscle were incubated in the presence of radiolabeled acetate, and the fat body showed the highest efficiency rate (around 47%) to convert the taken up acetate into lipids. The levels of de novo lipid synthesis in the flight muscle and ovary were very low. When 3H-palmitate was injected into the young females, its incorporation by the flight muscle was higher than by the ovary or the fat body. In the flight muscle, the 3H-palmitate was similarly distributed amongst triacylglycerols, phospholipids, diacylglycerols and free fatty acids, while in the ovary and fat body it was mostly found in triacylglycerols and phospholipids. The flight muscle was not fully developed after the molt, and at day two no lipid droplets were observed. At day five, very small lipid droplets were present, and they increased in size up to day fifteen. The diameter of the muscle fibers also increased from day two to fifteen, as well as the internuclear distance, indicating that muscle hypertrophy occurred along these days. The lipid droplets from the fat body showed a different pattern, and their diameter decreased after day two, but started to increase again at day ten. The data presented herein describes the development of the flight muscle after the final ecdysis, and modifications that occur regarding lipid stores. We show that, after molting, substrates that are present in the midgut and fat body are mobilized and directed to the ovary and flight muscle, for the adults of R. prolixus to be ready to feed and reproduce.
Lipids are an important class of nutrients for insects, as they are the main energy source during metamorphosis and crucial for survival and reproduction. Lipid reserves in insects are mostly accumulated during larval development and can be influenced by environmental factors such as diet and temperature. Genetic factors can also affect larval lipid content and composition. Larvae of the house fly, Musca domestica L. (Diptera: Muscidae), are a valuable emerging resource for the insect feed sector, fueling a growing interest in the factors regulating larval lipid content. We investigated whether strains of three geographical origins vary in ontogeny, quantity, and composition of stored lipids in response to temperature. Italian, Spanish, and Dutch house fly larvae were reared on a similar diet at 25 and 35 °C. Larval dry weight and total lipid content were determined in early‐, mid‐, and late‐third instars by extraction of soluble lipids. The fatty acid composition was analyzed in late‐third instars using an improved extraction and derivatization protocol. We found that strain, larval stage, and temperature affected larval dry weight and absolute and relative lipid content, with significant interaction effects between these three factors. All flies were reared in a common environment, indicating a genetic component to lipid storage. Analysis of lipid composition identified 11 fatty acids, including some rarely reported in the literature. Five fatty acids accounted for 80 and 81% of the total fatty acid methyl esters detected at 25 and 35 °C, respectively. An effect of temperature but not strain was evident on the composition of the fatty acids. The observed differences in lipid content among strains and temperature conditions could be of interest for commercial rearing of the house fly.
Odorant‐binding proteins (OBPs) play key roles in the perception of semiochemicals in insects. Several OBPs in insect olfactory systems have been functionally characterized, and they provide excellent targets for pest control. The functions of some OBPs that are highly expressed in the non‐sensory organs of insects remain unclear. Here, the physiological function of an OBP (OBP27) that was highly expressed in the non‐sensory organs of Spodoptera frugiperda was studied. OBP27 was nested within the Plus‐C cluster according to phylogenetic analysis. The transcription of OBP27 steadily increased throughout the development of S. frugiperda, and transcripts of this gene were abundant in the fat body and male reproductive organs. An OBP27 knockout strain with an early frameshift mutation was obtained using the CRISPR/Cas9 system. The development time of OBP27−/− larvae was significantly longer than that of other larvae. Both male and female OBP27 −/− pupae weighed significantly less than wild‐type (WT) pupae. In crosses of OBP27−/− males or females, the mating rate was lower and the mating duration was longer for OBP27−/− male–WT female pairs than for WT–WT pairs. By contrast, the mating rate, hatching rate, and number of eggs of OBP27−/− female–WT male pairs and WT–WT pairs were similar. These findings indicate that OBP27 plays an important role in the larval development and mating process in male adults. Generally, our findings provide new insights into the physiological roles of non‐sensory OBPs. This article is protected by copyright. All rights reserved
Premise:
Why have pollen grains evolved to be exceptionally large in some species? Pollen feeding hypothesis suggests that if the proportion of pollen amounts for feeding is reduced in a flower, the low allocation to pollen number would allow pollen grains to be larger.
Methods:
To examine whether species with large pollen grains experience low pollen consumption, the behavior of insects feeding on nectar and pollen was observed and pollen transfer efficiency was estimated for four visitor types in Geranium delavayi. To see whether bees actively collected pollen, the numbers of grains in pollen baskets and on the body were compared. Both nutritional value (total protein and lipid) and chemical defense (phenolic metabolites) in pollen against pollen feeders were measured.
Results:
Bumblebees and honeybees foraged for nectar, rarely groomed pollen into corbiculae, and had > 5× higher pollen transfer efficiency than smaller solitary bees and flies, which were pollen eaters that removed more pollen but deposited less. Pollen grains were characterized by low protein and high lipid content with a low protein-lipid ratio, an unfavorable combination for bumblebees. Three secondary metabolites were significantly higher in pollen grains (7.77 mg/g) than in petals (1.08 mg/g) and in nectar (0.44 mg/g), suggesting stronger chemical defense in pollen.
Conclusions:
Our results indicated that large bees took nectar but little of the nutritionally poor and highly toxic pollen. These data support one prediction of the pollen feeding hypothesis, that species with few and large pollen grains would also have low pollen consumption rates. This article is protected by copyright. All rights reserved.
Although increasingly used in animal feeding, the black soldier fly (Hermetia illucens - HI) and mealworm (Tenebrio molitor - TM) larvae and pupae require the characterization and modulation of their fat profile for use in the feed industry. In this study, we provide a comprehensive fatty acid profile of the total lipid triglycerides and phospholipids, and sterol composition. For a more detailed characterization of the nutritional properties, we defined the profile of esterified fatty acids (FAs) in the sn-2 position of the triglycerides, which represents the most adsorbed fraction by animals during digestion. Twenty-four batches (12 batches per species divided into 6 batches of larvae and 6 batches of pupae) of 70 subjects were used for the analysis. For each of the developmental stages, individuals in the intermediate stage were considered (2 months and 8 days for TM larvae and pupae respectively; 9 days and 7 days for HI larvae and pupae respectively). Some fatty acids (decanoic, lauric, or myristic acid) were more abundant in HI than in TM. These FAs were produced de novo, indicating that HI produce them from carbohydrates as a source of acetyl-CoA. Hermetia illucens showed a higher level of conjugated linoleic acid (CLA) isomers, a class of fatty acids with positive health effects. In contrast, TM showed a similar fatty acid profile to the plant lipid source (such as soy and sunflower) due to the high level of linoleic acid. Analysis of the triglyceride fraction showed a different affinity for the three glyceride positions. In particular, lauric acid, polyunsaturated fatty acids n-3 and CLA isomers esterified preferentially in sn-2, and therefore were the most adsorbed by the animal during digestion. As for the phospholipids, HI showed a higher level, above all in terms of the phosphatidylethanolamine fraction. Interestingly there was no sphingomyelin in the pupae of both species. The high level of phospholipids is a useful feature for the emulsion of fats in animal feed diets. Lastly, we observed a considerable amount of phytosterol in the sterol profile of both species, which makes these insects a valid alternative to other food sources of plant origin for animal nutrition. We believe that our findings provide new nutritional information for the use of TM and HI in the animal diet.
Thin layer chrom atography of retina extracts from Calliphora yielded, instead of retinal (or retinaloximes after NH2OH treatment) a considerably more polar aldehyde or its corresponding oximes. That these compounds originate from the chrom ophoric group of the visual pigment was shown by the occurrence of different stereoisomers in the extracts depending on the colour with which the intact visual pigment complex was previously illuminated. The absorbance maximum of the oxime found after blue illumination is the same as that of all-trans-retinal-oxime (356 nm). This spectral accordance means that previous spectral evidence for retinal as the chrom ophoric group of fly visual pigm ent is not conclusive. Flies raised on a carotenoid deficient diet enriched with the hydroxy-xanthophyll lutein possess a high visual pigment content. This points to a hydroxy- xanthophyll as a possible precursor of the chromophoric group.
The flight of an insect is of a very complicated and extremely energy-demanding nature. Wingbeat frequency may differ between various species but values up to 1000 Hz have been measured. Consequently metabolic activity may be very high during flight and the transition from rest to flight is accompanied by an increase of 50-100-fold in metabolic rate. Small mammals running at maximal speed and flying birds achieve metabolic rates exceeding resting levels by only 7-14-fold. The exaggerated metabolic rate during insect flight is not accompanied by an oxygen debt, which implies -apart from metabolic adaptations- ample availability of oxygen in the organs responsible for flight. Metabolic rate therefore can be estimated, apart from the depletion of fuel depots, by rates of oxygen consumption.
In view of the extremely high metabolic rates involved, insect flight offers a fascinating model system for studying metabolism during exercise, including its regulation by metabolic neurohormones. In our laboratory the African migratory locust, Locusta migratoria, well-known for its long-distance flights, is used as an internationally recognized model insect. The insect is mass-reared under controlled conditions; its size permits convenient handling in vivo and in vitro, while flight activity can be easily evoked. In addition, research on this pest insect may be of economical importance. A survey of the energy metabolism during locust flight is presented in Fig.1. Flight activity stimulates the neurosecretory adipokinetic cells in the glandular lobes of the corpus cardiacum, a neuroendocrine gland connected with the insect brain, to release peptide neurohormones, the adipokinetic hormones (AKHs). The target for these hormones is the fat body. Via signal transduction processes, the action of the hormones ultimately results in the mobilization of both carbohydrate and lipid reserves as fuels for flight. Carbohydrate (trehalose) is mobilized from glycogen reserves, implying hormonal activation of the key enzyme, fat body glycogen phosphorylase, by phosphorylation. Similarly, on the lipid side, sn-1,2-diacylglycerol (DAG) is mobilized from stored triacylglycerol (TAG), by hormonal activation of the fat body TAG lipase. The carbohydrate and lipid substrates are transported in the hemolymph to the contracting flight muscles. Carbohydrate provides most of the energy for the initial period of flight, whereas at a later stage, lipid substrate in the blood is increased and gradually takes over. The transport of DAG requires specific lipoprotein carriers (lipophorins) which differ in several respects from the lipoproteins in mammals, and act as a lipid shuttle. This review is focused on three interrelated topics, covering recent data on the biosynthesis and release of the AKHs, their signal transduction mechanisms in the fat body cells, and the changes in the lipophorin system induced by the AKHs during flight.
This chapter presents a historical and comprehensive review of the understanding of arachidonic acid and its oxygenated metabolites in insects and other arthropods. This chapter discusses prostaglandis and eicosanoids in insects. Eicosanoid is an umbrella term for all of the biologically active metabolites of arachidonic and two other C20 polyunsaturated fatty acids (PUFAs). Certain PUFAs are transformed into eicosanoids, which mediate a bewildering array of biological activities, many of which centre around signalling or regulating events within cells. The chapter discusses models of eicosanoid action. An appreciation of the roles of eicosanoids, such as prostaglandins (PGs) and related compounds, in various animal groups entails a broadly comparative physiology. Lying amid nutrition and physiology, arachidonic acid oxygenation involves three major biochemical pathways. The products of each major pathway are often themselves substrates of other pathways. The result is a plethora of oxygenated metabolites, each with a singular potential to exert a potent biological effect on cell function.
Revue chez les arthropodes des fonctions sur differents organes (muscles alaires, tissu adipeux) des hormones adipocinetiques. Comparaison interspecifique de la sequence en acides amines. Considerations sur l'evolution de cette famille de peptides
Insect flight is the most energy-demanding activity of animals. It requires the coordination and cooperation of many tissues, with the nervous system and neurohormones controlling the performance and energy metabolism of muscles, and of the fat body, ensuring that the muscles and nerves are supplied with essential fuels throughout flight. Muscle metabolism can be based on several different fuels, the proportions of which vary according to the insect species and the stage in flight activity. Octopamine, which acts as neurotransmitter, neuromodulator or neurohormone in insects, has a central role in flight. It is present in brain, ventral ganglia and nerves, supplying peripheral tissues such as the flight muscles, and its concentration in hemolymph increases during flight. Octopamine has multiple effects during flight in coordinating and stimulating muscle contraction and also energy metabolism partly by activating phosphofructokinase via the glycolytic activator, fructose 2,6-bisphosphate. One important muscle fuel is trehalose, synthesized by the fat body from a variety of precursors, a process that is regulated by neuropeptide hormones. Other fuels for flight include proline, glycerol and ketone bodies. The roles of these and possible regulation in some insect species are discussed.
Sterols are essential nutrients for grasshoppers, as well as all other insects, but metabolic constraints can limit which phytosterols support normal growth and development. In the current study, the generalist grasshopper Schistocerca americana was used to address two questions related to grasshopper sterol nutrition: (1) how does sterol quantity influence growth and survival, and (2) how do mixtures of suitable and unsuitable sterols at different concentrations influence growth and survival? Results from the first experiment indicated that this grasshopper species had a minimum sterol requirement of 0.05% dry weight; as sterol quantity increased above this concentration, however, survival and performance were not enhanced. Results from the second experiment revealed two novel aspects of sterol nutrition in grasshoppers: (1) when suitable sterols were limiting, most individuals could not use unsuitable sterols to meet the minimum sterol requirement (i.e. no sparing occurred), and (2) above a certain threshold, unsuitable sterols were deleterious even when suitable sterols were present at a concentration that alone permits normal growth and development. We discuss these physiological findings in terms of how sterol metabolic constraints in grasshoppers might influence foraging.
The metabolism of locust lipophorin A + during lipid delivery to the flight muscle and lipid loading at the fat body was studied in vitro. Protein C 2 was shown to be released upon hydrolysis of lipophorin A+-carried diacylglycerol by the flight muscle lipoprotein lipase. This/n vitro released protein C 2 was shown to reassociate with lipophorin Ay upon hormone-induced lipid mobilization from fat body in vitro. These results demonstrate the reversibility of the association of protein C 2 with lipophorin Ay and support the shuttle function of the protein components of locust lipophorin A + in lipid transport.
Vitamin K1 added to a basic diet for the house cricket, Acheta domesticus (L.), significantly improves growth of male and female larvae. Growth is significantly better with 18.7 μg K1/g than it is with an equimolar amount of vitamin E. Unlike vitamin E, however, vitamin K1 is without effect on reproduction. Vitamins K3 and K5, and coumarin, have no effect or a slightly inhibiting effect on growth, and no effect on reproduction.
Aphids of Schizaphis graminum (Rondani) (biotype C) reared on its host-plant, Sorghum bicolor (L.) Moench, sequestered campesterol, stigmasterol and sitosterol. Aphids reared for 72 hr on holidic diets supplemented with [4-14C]-sitosterol contained both [14C]-sitosterol and [14C]-cholesterol, indicating that these aphids are capable of dealkylation at C-24. When aphids were reared on artificial diets containing [2-14C]-mevalonic acid, no detectable amounts of radioactively labelled desmethyl sterols, nor metabolic intermediates in sterol synthesis (i.e. squalene, 2,3-oxidosqualene, 4,4-dimethyl and 4-monomethyl sterols) were found to accumulate in their tissues. The relevance of these findings to previous research suggesting the ability of aphids, via their symbiotes, to synthesize sterols is discussed.
The interrelationships of 5-HT receptors and the increased fluid secretion by isolated salivary glands of Calliphora have been studied using pharmacological techniques. Removal of the 5-OH group (tryptamine) or displacement to position 6 (6-HT) results in a decrease in potency but no change in intrinsic activity of the hormone whereas altering the ethyl amine side chain (5-OH tryptophan) results in a decrease in both potency and intrinsic activity. Removal of the 5-OH group and alteration of the side chain (gramine and tryptophan) results in a total loss of activity. Gramine and tryptophan behave as competitive antagonists of 5-HT.Prostaglandin E1 (PGE1) was found to be a non-competitive inhibitor of 5-OH tryptophan and theophylline whereas the response to 5-HT and cyclic AMP was only slightly diminished indicating a ‘receptor reserve’ for 5-HT.Saturating concentrations of gramine and tryptophan potentiate theophylline revealing a ‘threshold’ for the mediation of the response. It is concluded that 5-HT derivatives are capable of producing graded effects on adenyl cyclase both above and below the range of enzyme activity which evokes graded changes in fluid secretion.
The principal site of cholesterol absorption was studied in a number of insects using 3H-cholesterol mixed with the diet of the insects. In omnivorous insects (Gryllodes sigilatus and Camponotus compressus) and a carnivorous insect (Dytiscus sp.) cholesterol was absorbed in the foregut, predominantly in the crop. In the phytophagus insects and some others (Schistocerca gregaria, Hieroglyphus nigrorepletus, Dysdercus koenigii, Belostoma sp., Lucilia sp., Apis sp. Mylabris phalerata and larvae of Papilio demoleus, Prodenia litura, and Earias fabia) the midgut was the main site of cholesterol absorption.
The sterols of six species of Hymenoptera including two phytophagous species (Apis mellifera and Megachile rotundata) and four omnivorous species (Dolichovespula maculata, Vespula maculifrons, Formica exsectoides, and Solenopsis invicta) were isolated and identified. The two phytophagous species of bees have in common relatively high levels of 24-methylenecholesterol and very low levels of cholesterol (<1% of total sterols). The isofucosterol content (40.7%) of M. rotundata was nearly three times that of A. mellifera, but overall utilization of dietary sterols in the two species is similar in that neither is able to convert C28 and C29 phytosterols to cholesterol. All four omnivorous species are predatory to some extent, and the fact that their usual dietary sterols include high levels of chlosterol is reflected in the sterols isolated from these species, which contain 45–81% cholesterol. All six hymenopteran species appear to utilize dietary sterols for structural needs with little or no metabolic modification of the steroid structure.
The de novo biosynthesis of linoleic acid (9,12-octadecadienoic acid), generally considered an essential dietary nutrient for animals, has been demonstrated in 15 insect species representing four orders. Two of these species were also shown to further elongate and desaturate linoleic acid to form arachidonic acid, implying the ability to insert double bonds on both sides of the Δ position of oleic acid (9-octadecenoic acid).
1.1. Larval Musca domestica lipophorin biosynthesis was studied in vitro.2.2. The newly synthesized lipophorin has a density a little lower than the circulating lipophorin after 1 hr of incubation. After 3 hr of incubation the fat body cells transfer lipids to the lipophorin that attains the density of circulating lipophorin.3.3. The lipophorin synthesized in vitro is identical to circulating lipophorin in density and in electrophoretical behavior.4.4. However these two molecules must have differences since the circulating lipophorin transfers lipids to fat body cells while the synthesized in vitro does not.5.5. The biosynthesis of Musca lipophorin shows differences with the Manduca sexta lipophorin biosynthesis.
The metabolism of locust lipophorin A+ during lipid delivery to the flight muscle and lipid loading at the fat body was studied in vitro. Protein C2 was shown to be released upon hydrolysis of lipophorin A+-carried diacylglycerol by the flight muscle lipoprotein lipase. This in vitro released protein C2 was shown to reassociate with lipophorin Ay upon hormone-induced lipid mobilization from fat body in vitro. These results demonstrate the reversibility of the association of protein C2 with lipophorin Ay and support the shuttle function of the protein components of locust lipophorin A+ in lipid transport.
32P-Labelled midguts (32P-midguts) of Rhodnius prolixus females were incubated in the presence of nonradioactive purified lipophorin and the release of radioactivity to the medium was analysed. The radioactivity found in the medium was associated with lipophorin phospholipids. When the 32P-midguts were incubated in the absence of lipophorin, no 32P-phospholipids were found in the medium. Comparative analysis by thin-layer chromatography of 32P-phospholipids derived from metabolically labelled 32P-midgut or lipophorin particles after incubation with 32P-midgut showed some differences, revealing a possible selectivity in the process of phospholipids transfer. The transfer of phospholipids to lipophorin was linear with time up to 45 min, was saturable with respect to the concentration of lipophorin, and was half-maximal at about 5 mg/ml. The binding of 32P-lipophorin to the midgut at O°C reached the equilibrium at about 1 h of incubation. The binding of 32P-lipophorin was inhibited by an excess of nonradioactive lipophorin, which suggests a specific receptor for lipophorin. The capacity of midguts and fat bodies to transfer phospholipids to lipophorin varied during the days following the meal. When lipophorin enzymatically depleted of phospholipids by treatment with phospholipase A2 was incubated with 32P-midguts, the same amount of phospholipids was transferred, indicating a net gain of phospholipids by the particle. © 1995 Wiley-Liss, Inc.
Dietary lipids and carbohydrates ingested by insects vary widely depending on the foods consumed. Approximately half the known insect species are phytophagous, consuming photosynthetic or other plant tissues. Insect and angiosperm coevolution has also led to a more specialized type of herbivory, namely the use of nectar and pollen as sources of sugars and amino acids. Insect carnivores feed on animal material ranging from insect tissues to mammalian blood.
A hemolymph lipid transfer protein (LTP) was isolated from the tobacco hornworm, . LTP catalyzes net lipid transfer between isolated hemolymph lipoproteins . An isolation procedure employing density gradient ultracentrifugation and gel permeation chromatography produced a purified protein. LTP is a very high density lipoprotein with a particle Mr > 500,000. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that LTP is comprised of two apoproteins: apoLTP-I (Mr ∼ 320,000) and apoLTP-II (Mr ∼ 85,000). LTP may have a physiological role in altering the lipid content and composition of the major hemolymph lipoprotein, lipophorin.
The prothoracic glands of Manduca sexta synthesize dehydroecdysone, which is rapidly converted to ecdysone through the mediation of a hemolymph enzyme, a 3 β-forming-3-ketosteroid reductase. The hemolymph protein fraction (HPF) containing this enzyme was obtained from diapausing and non-diapausing pupae, isolated abdomens, surgically manipulated pupae, etc., and in all cases had the capacity to affect the conversion of dehydroecdysone to ecdysone. The enzyme is heat labile, is inactivated by trypsin, and has a molecular weight of between 20,000 and 30,000. The data indicate that the conversion of dehydroecdysone to ecdysone exhibits linear kinetics and may be dependent on both the enzyme concentration and the concentration of NADPH at the beginning of the reaction but may be limited by the absolute amount of reducing equivalents after 10 min, under the experimental conditions utilized. The capacity of the enzyme to reduce dehydroecdysone was titered in the hemolymph during the last larval instar and during prepupal and pupal life with maximum capacity exhibited at the beginning of the instar, on day 8 of larval life and at day 1 of pupal life. Even at its lowest point at day 5, 1 ml of hemolymph was able to convert 77 pmol (∼35 ng) dehydroecdysone to ecdysone in 1 min. These results require a new interpretation of the control of molting in the Lepidoptera.
The major insect hemolymph lipoprotein, lipophorin, was isolated from adults of eight insect species representing seven insect orders. Sodium dodecyl sulfate polyacrylamide gel electrophoresis was used to compare their respective apoprotein components. In all species examined lipophorin was composed of at least two apoproteins, apolipophorin I (Mr ∼ 250,000) and apolipophorin II (Mr ∼ 78,000), and two species had a third apoprotein, apolipophorin III (Mr ∼ 17,000). The density of each isolated lipophorin was determined from the refractive index of KBr following density gradient centrifugation. Immunoblotting with anti-larval Manduca sexta apolipophorin I and II of the apoproteins separated by SDS-PACE indicated cross reactivity between anti-M sexta apoLp-ll and apoLp-ll in all species tested. Anti-M sexta apoLp-l exhibited no cross reactivity for any species tested. Fluorescent lectin staining of the apoproteins separated on SDS-PAGE gels revealed the presence of covalently bound carbohydrate residues.
This chapter discusses the structure and function of major groups of hemolymph proteins that are common to all insects, storage proteins, lipoproteins, vitellogenins, and inducible antibacterial proteins. It also discusses some proteins and peptides that are present in smaller amounts, sometimes occurring only in a few insect species. With the development of microsequencing techniques that can provide information about the sequence of amino acids at the N-terminal end of an intact protein on a sample of less than 20 picomoles, it has become feasible to use one- or two-dimensional polyacrylamide gel electrophoresis (PAGE) a the protein purification method of choice. In many cases, proteins can be transferred directly from gels to derivatized paper or other media and spots cut from the medium can be inserted directly into the sequencer. If necessary, proteins on the medium can be cleaved to peptides, which can be separated by high-pressure liquid chromatography (HPLC) or by PAGE.
Inhibition of eicosanoid biosynthesis in in vitro preparations of Malpighian tubules isolated from adult ants, Formica polyctena, reduced basal fluid secretion rates. Inhibition of total eicosanoid biosynthesis with 100 μM 5,8,11,14-eicosatetraynoic acid (ETYA) and inhibition of prostaglandin biosynthesis with 100 μM indomethacin strongly reduced basal fluid secretion. The lipoxygenase inhibitor esculetin and the epoxygenase inhibitor SKF-525A did not influence fluid secretion rates during its application, although it blunted the cAMP effect somewhat after washout. These findings indicate that prostaglandins are involved in regulating fluid secretion rates in ant Malpighian tubules. Although stimulation by cAMP was somewhat reduced, the influence of ETYA and indomethacin on fluid secretion rates did not prevent adenosine 3′,5′-cyclic monophosphate from exerting its secretagogue effect. This indicates that the eicosanoid biosynthesis inhibitors acted in a physiological way on the Malpighian tubules.The eicosanoid-precursor polyunsaturated fatty acid, arachidonic acid, is present in phospholipids of Malpighian tubules. This finding indicates that substrate for prostaglandin biosynthesis is available.
Determinations of carbohydrases, proteases, carboxylesterases and phosphatases in the midgut cells and in the luminal spaces outside and inside the peritrophic membrane of Rhynchosciara americana larvae have been carried out. The data show that alpha-amylase, cellulase and proteinases are present in cells, ecto- and endoperitrophic spaces; aminopeptidases and trehalase in cells and ectoperitrophic space; and finally disaccharidases (except trehalase), carboxypeptidases, dipeptidases, carboxylesterases and phosphatases only in cells. The results support the conclusion that digestion takes place in three spatially organized steps. The first one occurs inside the peritrophic membrane and comprises the dispersion and/or decrease in molecular weight of the food molecules. The second is the hydrolysis of the polymeric food molecules in the ectoperitrophic space to dimers and/or small oligomers. Finally, terminal digestion occurs in the midgut caeca and posterior ventriculus cells by enzymes presumed to be plasma membrane bound. The existence of two extracellular sites for digestion in R. americana is considered to be an adaptation to conserve secreted enzymes, since only those penetrating the endoperitrophic space are lost quickly in the faeces.
The name Lipophorin (Gk. lipos, fat; phoros, bearing) is proposed as a generic term for the class of insect haemolymph lipoproteins that serve to transport lipids between organs of absorption, storage and utilisation.
The interaction of locust high density lipophorin (HDLp) with pieces of fat body tissue was studied at 33°C using a radiolabelled ligand binding assay. Under the assay conditions, binding of tritium-labelled HDLp ([3H]HDLp) was demonstrated to correlate linearly with tissue concentration up to ∼ 7 mg of fat body protein per ml of incubation medium. The [3H]HDLp binding that was displaceable by a 20-fold excess of unlabelled HDLp (which is an approximation of the specific binding) reached equilibrium after ∼ 2 h, whereas low levels of non-displaceable binding increased linearly during this time interval. Analysis of the concentration dependent total binding of [3H]HDLp revealed the presence of a specific binding site with an equilibrium dissociation constant of Kd = 3.1 (±0.5) × 10−7 M and a maximal binding capacity of 9.8 (±0.5) ng μg−1 tissue protein. Competition experiments demonstrated that the affinity of unlabelled HDLp for the binding site is similar to the affinity of [3H]HDLp. Unlabelled low density lipophorin (LDLp), however, was shown to have an approx. 20-fold lower affinity for the binding site.
The fate of radiolabelled campesterol, sitosterol and 24-methylenecholesterol fed in chemically-defined diets to honey bee (Apis mellifera L.) workers was determined. At various intervals, sterols of prepupae, newly emerged adults and queens were analyzed qualitatively, quantitatively and radiochemically and it was determined that there was not sufficient radioactivity associated with cholesterol and/or desmosterol in any of the samples to verify that any of the three C28 and C29 sterols was dealkylated and converted to cholesterol. Similarly, there was no evidence for the conversion of campesterol or sitosterol to 24-methylenecholesterol. It was concluded that the major portion of the sterols incorporated into the tissues of the brood larvae originated from the worker bees used to establish the colony. There is good evidence supporting the premise that the workers can make available sterols from their endogenous pools to the nutrient in the hive and that they can replenish these sterols with those from the artificial diet. The queen is also able to replenish sterols utilized in egg production from those obtained by the workers from the artificial diet, and at the end of nine weeks queens contained more than four times as much sterol, on a ‘μg sterol per g fresh weight’ basis, than was found in fertile queens at the beginning of the test period.
Since they are unable to biosynthesize sterols, many phytophagous and omnivorous insects satisfy their cholesterol requirement
by side chain dealkylation of the C-24 alkyl group of dietary C28 and C29 phytosterols. However, not all insects that can dealkylate the phytosterol side chain produce cholesterol. In addition, certain
insects,e.g., some Hymenoptera, Hemiptera, and Diptera, are unable to dealkylate the sterol side chain. Although C27 ecdysteroids (molting hormones), which are biosynthesized from cholesterol, are the major ecdysteroids in most insects, many
of those species that are unable to dealkylate phytosterols utilize campesterol as a precursor for the C28 ecdysteroid makisterone A. The considerable diversity of steroid utilization between certain insect species makes it difficult
to generalize about insect steroid biochemistry. The ability to disrupt certain unique aspects of steroid utilization and
metabolism in insects might be exploited for developing new insect control technology.
Les larves et les adultes de la bruche du haricot se nourrissent de deux types d'aliments différents, mais proches en ce qui concerne la composition en hydrates de carbone: les larves consomment des graines de Phaseolus vulgaris et P. coccineus , les adultes s'alimentent principalement avec le pollen de diverses plantes.
L'activité des larves et des adultes a été étudiée sur 22 substrats différents, en vue de préciser les caractéristiques de leur équipement osidasique. Les recherches ont montré que les larves et les adultes possèdent un équipement très important en α‐ et β‐glucosidases, en α‐ et β‐galactosidases, ainsi que des activités très importantes sur certains polysaccharides, notamment l'amidon et la pectine, mais l'activité est faible sur les hémicelluloses étudiées, notamment la xylane, l'arabinogalactane et la glucomannane. Les activités sur la carboxyméthylcellulose et la cellulose, ainsi que l'inuline, sont nulles.
La corrélation étroite entre la composition en hydrates de carbone de la nourriture et les activités glycosidasiques du canal alimentaire chez les larves et les adultes permet une utilisation optimale des ressources trophiques en hydrates de carbone. Le parallélisme frappant entre le système glycosidasique des larves et celui des adultes a pour explication la ressemblance entre la composition en carbohydrates du pollen et celle de l'endosperme de haricot.
Summary
Study of glycosidase activities of the digestive tract of the larvae and adults in Acanthoscelides obtectus ( Coleoptera: Bruchidae )
Adults and larvae of Acanthoscelides obtectus eat two different types of food, similar in carbohydrate composition: larvae eat seeds of Fhaseolus vulgaris and P. coccineus , adults eat principally pollen of various plants. The authors have studied the digestive activity of larvae and adults on 22 different sugars, in order to investigate activity of their glycosidase enzymes. Larvae and adults have a very important complement of α‐ and β‐glucosidases, α‐ and β‐galactosidases, and very high activity against certain polysaccharides, notably starch and pectin. The activity is weak on the hemicelluloses tested, notably on xylan, arabinogalactan and glucomannan. No activity is found on carboxymethylcellulose, cellulose and inuline.
The close correlation between the carbohydrate composition of the food and the glycosidase activity of the alimentary canal in both larvae and adults enables optimal utilization of carbohydrate resources. The striking parallel between the glycosidase systems of adults and larvae is explained by the similar carbohydrate composition of pollen and bean endosperm.
Inhibition of eicosanoid biosynthesis in in vitro preparations of Malpighian tubules isolated from adult females of the yellow fever mosquito Aedes aegypti substantially reduced basal fluid secretion rates. The phospholipase A2 inhibitor 5,8,11,14-eicosatetraynoic acid (ETYA) and the cyclooxygenase inhibitor indomethacin far more effectively reduced basal fluid secretion than the epoxygenase inhibitor SKF-525A. The lipoxygenase inhibitor esculetin had no effect on basal fluid secretion. These findings indicate that products of cyclooxygenase are involved in regulating basal fluid secretion in Malpighian tubules. The effects of indomethacin were expressed in a dose-dependent manner, further indicating that eicosanoids are physiologically involved in fluid secretion. The effects of cyclooxygenase inhibition on reduction of basal secretion rates have not prevented adenosine 3′,5′-cyclic monophosphate (cAMP) from exerting its secretagogue effect.These results strongly support the hypothesis that eicosanoids, especially prostaglandins, are involved in Malpighian tubule function in A. aegypti. Recognition that eicosanoids may be involved in regulating basal fluid secretion rates introduces a previously unrecognized tier of regulatory physiology into insect renal function.
Metabolic pathways in the midgut cells of last instar larvae of Pieris brassicae were labeled with glycerol, galactose, and choline to examine the role of enterocytes in nutrient metabolism during feeding. The data support the view that the caterpillar midgut is a significant site of intermediary metabolism. Dietary glycerol was used in midgut cells in the synthesis of 1,2-diacylglycerol and other glycerolipids (indicating the presence of the glycerol phosphate pathway), as well as in the synthesis of amino acids. Gluconeogenesis and glycogenesis from glycerol occurred slowly in midgut tissue, but readily in peripheral tissues. Absorbed galactose was converted in midgut cells to glucose, glycogen, glycolytic intermediates, lipids, and amino acids. The data show rapid transfer of the water-soluble metabolites into the hemolymph and other tissues. The results support a hypothesis that a major route of acylglycerol transfer across the midgut epithelium is via transient synthesis of triacylglycerol in midgut cells. Data on glycerophospholipid absorption suggest that a significant proportion is taken up into the enterocytes in the lyso-form.
The digestion, absorption, and transport of [4-14C]cholesterol and glycerol tri [1-14C]oleate were examined in the midguts of fifth instar larvae of the southwestern corn borer, Diatraea grandiosella. The results indicate that the anterior region of the midgut is the most active zone for the absorption and transport of lipids into the haemolymph. The middle and posterior regions of the midgut appear to serve as temporary storage sites for absorbed lipid. Cholesterol was absorbed into the midgut cells without prior esterification and released into the haemolymph as free sterol. Although absorbed sterol was not esterified in the anterior region of the midgut, a substantial portion was esterified in the middle and posterior regions. Analysis of midgut contents and faeces showed that triolein was hydrolyzed in the lumen. Free fatty acids and unhydrolyzed triolein were the main labelled lipids in the faeces. In the midgut tissue radioactive [14C] from triolein was incorporated into phospholipids and triglycerides. The anterior region had the highest titre of labelled phospholipids, diglycerides and free fatty acids, and the middle and posterior regions had the highest titre of labelled triglycerides. The results suggest that free fatty acids and possibly diglycerides are absorbed. Diglycerides were the major labelled lipid in the haemolymph.
[3H] or [14C]cholesterol was administered to Manduca sexta larvae by injection and the prothoracic glands of the injected animals were then incubated in vitro. Labelled steroids in the glands and medium were analyzed by reverse-phase and normal phase high-performance liquid chromatography, and differential radioimmunoassay, and the data revealed the conversion of the labelled cholesterol to 7-dehydrocholesterol and then to ecdysone, 26-hydroxyecdysone and a less polar ecdysteroid with a modified A-ring. Similar, but more efficient incorporation of radiolabeled cholesterol into 7-dehydrocholesterol and ecdysteroids was attained by including the [3H]cholesterol in the incubation medium when prothoracic glands were incubated in vitro. Analysis by gas-liquid chromatography of the content of endogenous cholesterol and 7-dehydrocholesterol in the prothoracic glands during the 5th larval instar revealed changes in temporal accord with the production of ecdysteroids by these glands, the ratio of the two steroids being consistent with data obtained from the radiotracer studies. By incubating prothoracic glands with [3H]7-dehydrocholesterol, it was demonstrated that 7-dehydrocholesterol is not reduced back to cholesterol and that the former is an obligatory intermediate in ecdysteroid biosynthesis. The principal component of the A-ring modified ecdysteroid peak is 3-dehydroecdysone, a putative secretory product of the prothoracic glands and a possible immediate precursor of ecdysone.
Immunocytochemistry using affinity-purified polyclonal antilipophorin revealed extracellular and intracellular locations of lipophorin in the fat body of dragonfly larvae. Lipophorin was associated with the external surface of the superficial and lateral plasma membranes which are directly exposed to the haemolymph. This location probably plays a role in the extracellular lipid-loading and unloading of lipophorin. Lipophorin was detected in the endoplasmic reticulum, Golgi apparatus and small vesicles located in the trans Golgi network region. These locations were interpreted as the secretory pathway of nascent lipophorin. Lipophorin was localized in various membrane-bound compartments which were identified as endosomes using biotinyl lipophorin and horseradish peroxidase as endocytotic markers. These results clearly suggested that circulating lipophorin was endocytosed by the adipocytes. Lipophorin endocytosis might serve the removal and lysosomal degradation of old lipophorin and/or provide an additional or alternative intracellular recycling mechanism of lipid-loading and unloading.
Many advances in arthropod sterol metabolism, as it relates to ecdysteroid biosynthesis, have been made in the past 10 yr. The sterol 24-dealkylation system, present in the midgut of many species, is entirely absent in some members of at least four insect orders and the prothoracic glands of Manduca sexta. While Δ5-sterols are precursors in arthropod ecdysteroid biosynthesis, the Δ7-sterol, lathosterol, is the precursor in at least some plants. 7-Dehydrosterols are converted directly into ecdysteroids by insect prothoracic glands and ovaries, as well as crustacean Y-organs. Conclusive evidence for many potential mechanisms of sterol 7,8-dehydrogenation and conversion of the Δ5,7-sterols to 2,22,25-trideoxyecdysteroids is still lacking, though circumstantial evidence for a 5,6-epoxy-Δ7-sterol is discussed. The physiological relevance of 3-dehydroecdysteroids in some insects has only recently been appreciated. The sterol 7,8-dehydrogenating enzyme, the sequential terminal hydroxylases and ecdysone 20-monooxygenase all exhibit properties of cytochrome P-450 enzymes. The lack of tissue and substrate specificity reported for the terminal hydroxylations of exogenous substrates suggests that non-specific hydroxylases may be involved. Extensive pharmacological investigations of ecdysone 20-monooxygenase continue, and efforts toward the isolation and sequencing of this enzyme are underway. Developmental correlations suggest that the sterol 7,8-dehydrogenase and terminal hydroxylases in Manduca prothoracic glands are not regulated by prothoracicotropic hormone, in contrast to the utilization of 7-dehydrocholesterol. In crustaceans, the terminal hydroxylases are influenced by molt inhibiting hormone.
Radioactive oleic acid orally infused into dragonfly larvae (Aeshna cyanea) was recovered in the haemolymph in the esterified form as diacylglycerol which was transported by lipophorin. Radioactive diacylglycerol was released in vitro into the surrounding medium from the isolated, ligated midgut which had been preloaded in vivo with radiolabelled oleic acid. The release was largely dependent on the temperature and the presence of haemolymph in the incubation medium. On the other hand, the ligated midgut isolated from fasting larvae, was also able to absorb radioactive diacylglycerol from the haemolymph and to further esterify it to triacylglycerol. These results demonstrate that the midgut epithelium cannot only release but also absorb diacylglycerol at the basal side, which strongly suggests that both lipid-loading and unloading of lipophorin occur in the midgut probably in dependence of physiological conditions.Lipophorin penetrated across the basal lamina into the basolateral intercellular clefts of the midgut epithelium as evidenced by immunocytochemistry on the light and electron microscopic level, using affinity-purified polyclonal antibodies against lipophorin. The apicolateral intercellular clefts, i.e. the sites of the smooth septate junctions, and the intercellular clefts between the undifferentiated cells of the regeneration nidi remained unlabelled by antilipophorin. Incubation experiments with fluorescently labelled lipophorin suggested that lipophorin of the intercellular clefts was exchanged with lipophorin of the circulating haemolymph.Although the enterocytes showed clear endocytotic activity at the basolateral plasma membranes when incubated with horse radish peroxidase, lipophorin was not detected inside the cells by immunocytochemistry. Consequently, indications of lipophorin secretion and internalization were lacking.These results support the conclusion that lipid-loading and unloading of lipophorin occur extracellularly along the basolateral plasma membranes of the differentiated absorptive enterocytes.
Aposymbiotic Xyleborus ferrugineus utilized cholesterol or lanosterol as a sole source of sterol for production of eggs and hatching of larvae, but failed to pupate during consecutive broods or generations in diets with such sources of sterol. The insects produced several broods or generations of progeny that pupated and formed normal adults when ergosterol or 7-dehydrocholesterol was the sole source of sterol. Lumisterol, or vitamin D2 or D3, was antagonistic to progeny production or survival.
Oocyte development in Manduca sexta involves the deposition of large amounts of lipoprotein-derived lipid. One source of this lipid is hemolymph high-density lipophorin-adult (HDLp-A) which, upon entry into the oocyte, is transformed into a lipid and apolipophorin III deficient product particle, egg very-high- density lipophorin (VHDLp-E; density= 1.24 g/ml; Kawooya et al. (1988) J. Biol. Chem. 263, 8740–8747). An in vitro model of this transformation has been established using human low-density lipoprotein (LDL) as acceptor of HDLp-A associated lipid in a reaction catalyzed by isolated M. sexta hemolymph lipid transfer particle (LTP). Facilitated vectorial net transfer of lipid from HDLp-A to LDL resulted in formation of a very-high-density lipophorin (VHDLp) product with a density and apolipoprotein content similar to that of VHDLp-E. Lipid was found to comprise 25% of the VHDLp particle mass, whereas over 50% of HDLp-A mass is lipid. Based on these observations it was hypothesized that a lipid transfer factor may be present in M. sexta oocytes and function in the transformation of HDLp-A to VHDLp-E in vivo. Transfer activity was present in the buffer soluble fraction of oocyte homogenates and purification of the active material revealed a catalyst with electrophoretic and immunological properties identical to hemolymph LTP. Incubation of 125I-HDLp-A with an M. sexta oocyte homogenate resulted in transformation of the radiolabeled lipoprotein to a density corresponding to that of VHDLp-E. When the incubation media was preincubated with anti-LTP IgG this conversion was inhibited to a large extent. Inhibition was relieved, however, by addition of exogenous LTP. The results provide the first demonstration of M. sexta LTP in a tissue other than hemolymph and support the concept that LTP-catalyzed lipid transfer plays an integral role in the conversion of HDLp-A to VHDLp-E in vivo.
The source of the lipophorin present in the larval haemolymph of the southwestern corn borer, Diatraea grandiosella, was examined in vitro. Although lipophorin was shown to be one of several proteins released from cultured fat body and midgut, only fat body was shown to synthesize lipophorin. Fat body, incubated in a medium containing [3H]leucine, was shown to release radiolabelled lipophorin using immunoprecipitation. Similar studies using midguts incubated in a medium containing [3H]leucine did not reveal any synthesis of lipophorin. Lipophorin was isolated by density-gradient ultracentrifugation from media in which the fat bodies of about 600 diapausing larvae had been incubated for 4 hr. The isolated lipophorin had a peak density of 1.11 g/ml, and contained various lipids including diacylglycerol, triacylglycerol, sterol, hydrocarbon, free fatty acid, phosphatidyl choline, phosphatidyl ethanolamine and sphingomyelin.
The carbohydrase activities present in freeze-dried extracts of the alimentary tract of Locusta have been surveyed using natural and synthetic substrates and qualitative detection methods. A range of polysaccharidases was demonstrated including amylase, (weak) cellulase, dextranase, hyaluronidase, laminarinase, and xylanase, but there was no evidence of alginase, chitinase, 1,3-α-glucanase, inulinase, lysozyme, or pectinase.Almost all oligosaccharides and glycosides tested were hydrolysed, demonstrating the presence of α- and β-glucosidase (including isomaltase and trehalase), α- and β-galactosidase, α- and β-mannosidase, α- and β-xylosidase, β-glucuronidase, β-N-acetylhexosaminidase, and β-fucosidase, but no β-fructosidase was detected. α- and β-l-Fucosidase and α-l-arabinosidase activities were present but there was no evidence of α-l-rhamnosidase or β-l-arabinosidase. These observations are related to the diet and nutrition of Locusta and compared with the carbohydrase complements reported for other acridids.